What's your best alternate history utopia?

• The CIA didn't support the 1953 Iranian coup d'état. Instead, the Shah continued its process of political liberalization. By 2021, Iran has become a shining example of liberal Islam, with ripple effects on the surrounding region.
• Much of education is rote memorization. The backbone of rote memorization should be spaced repetition software instead of paper assignments and paper-like assignments. In particular, spaced repetition software with judicious use of machine learning on the backend. Technically this breaks the rule of "Same level of technology as today" but I feel it should count on the grounds that I am personally inventing this technology using off-the-shelf infrastructure.
• Wider (but not total) spread of religions promoting vegetarianism, kosher and halal.
• Redesign US cities by reducing free parking, increasing bicycle lanes and eliminating zoning laws that separate work from home.
• Everyone (worldwide) drives on the same side of the road.
• Electrons are positively charged. Protons are negatively charged. Positrons are called negitrons.
• Don't kill all the passenger pigeons, dodo birds and Galápagos tortoises. Eliminate the social prestige of eating endangered species.
• Establish an effective international governing body for maximizing the sustainable harvesting of oceanic fish.

The FairTax proposal of 1999 rapidly gained steam among the public due to Steve Jobs embracing it and touting how all sides would benefit, through a groundbreaking commercial campaign which made it obvious the income tax system benefited tax lawyers above all others. Politicians on all sides found themselves forced to support it or face the wrath of constituents. The bill passed, and America prepared for the century-old income tax system to be replaced with something modern and computerized.

Starting on Jan 1, 2001, every American citizen received a monthly tax rebate of the exact same fixed dollar amount instead of a yearly tax refund. (They also got their final income tax refund or made their final income tax payment around April.) Some people complained, but most people simply put it in their savings or checking accounts and hailed the end of the FICA payroll tax.

When the planes knocked down the World Trade Center towers on September 11, 2001, a recession started. But a marvelous thing happened: it didn't hurt the underclasses as much as previous recessions. The monthly "prebate" acted as a guaranteed income stream for people out of work, and the burden on unemployment and welfare systems was substantially reduced. The tax burdens on small businesses were not as onerous, because the big companies that could pay for legislative loopholes in the past didn't make out like bandits and leave small business to pay the tab. Used goods such as thrift stores boomed. Even as income inequality rose, standards of living rose for the lower classes.

As the country's economy rebuilt, the startlingly positive outcome resulted in numerous books and papers hailing the FairTax's success. The prebate had functioned as a "national dividend" which some called "universal basic income." A side effect was noted: the national treasury had been decoupled from labor. The futurists who'd been warning of automation's ills realized that half of the problem had been solved.

Another startling reform gained steam: universal welfare. The plan was to replace all means-tested welfare with a flat welfare check for all, spending on the people an amount that would have gone to bureaucrats to prevent those well-off from receiving public funds that had been extracted from their businesses by taxation.

It passed in 2006, and the income went through the same channels (paper checks and direct deposit) that people received the FairTax. Individual housing became more affordable for all families of every background.

There was no crash in 2008.

The foreclosures weren't as severe, and the assets never became toxic. Instead, America started paying down its debt, as the more people spent on consumer goods and services, the more taxes the government collected. Other countries started adopting similar programs, and similarly thriving.

Income inequality began being seen as a good thing, because the "whales" paid for everything. The more the billionaires thrived, the more the people got.

Cribbing from my answer to Top Time Travel Interventions [LW(p) · GW(p)], 

Voting theory got started earlier and got further. Bentham, Condorcet, and Borda all talked more, and more publicly. By the time of the founding fathers of the United States of America, better voting methods than plurality were known, and known more fully. Democracy in the USA is set up with a better voting method, and this becomes the template for better methods in other democracies around the world.

The USA never develops a two-party system, instead developing a multi-party system which represents many viewpoints. Politics is overall more sane, as it depends less on us-vs-them mentality.

As a result of saner and better politics, all manner of better policies get implemented. When economics gets good at giving advice, governments get good at listening.

(Perhaps a bit optimistic. And not nearly enough detail.)

ETA:

Public education develops along a different path, which keeps certification authorities separate from educators. This means it's rarely necessary to take a class if you could already pass the final exam. There's still a rat-race for certification (employers still look at certification as a sign of employee capability, so, you still get the general public competing for who can get more certification, even when it's unrelated to the jobs they eventually get); but, smart people can much more easily skip past a bunch of stuff, study on their own, etc rather than wasting time sitting in classes that aren't doing them any good.

The Bretton Woods conference adopted Keynes' Bancor as the currency of international trade rather than the US dollar.  This encouraged industrial development much more evenly across the world and prevented large amounts of the imbalanced financial flows that have given certain countries exorbitant power over others, driven others into the resource trap, and driven still others into foreign-denominated debt spirals.

One Eliezer, a member of an obscure tribe in the Middle East, found himself dissatisfied with all religion, and especially that of his own people. He pondered deeply over the question of how to attain real knowledge of the world, and wandered through many countries observing how such things proceeded there. Eventually, having arrived at tried and tested conclusions about what methods systematically lead towards truth, he fetched up in ancient Greece in the time of the great philosophers. Here, it seemed, there might be some few people capable of understanding what he had discovered. He was successful in persuading them to take seriously the idea of working with their own hands to experiment and observe, to "entangle themselves with the world", and got SCIENCE!! started two thousand years earlier.

According to Plutarch in "The Obsolescence of Oracles", when Eliezer visited the oracle at Delphi it prophesied, "HE IS HERE. THE ONE WHO WILL TEAR APART THE VERY STARS IN HEAVEN. HE IS HERE. HE IS THE END OF THE WORLD." The oracle never spoke again.

Somehow (don't ask me how...) humanity developed a much stronger shared identity and the dominant 'affiliation' most people have is to all of humanity.

I think it's obvious this would change just about everything else...

Hopefully we actually get there in reality one day.

A major nuclear power plant accident doesn't happen (no Three Mile Island, no Chernobyl, no Fukushima). Nuclear power remains popular despite continual objections from a small contingent of radical activists. As a result, we stop using other sources of power and most climate change effects are avoided. Also, we have abundant power to do cool things with.

How far back  can I change the institutions? Once you change institutions enough you do change the technology and perhaps the psychology. Something like the Glorious Revolution happening in Rome or any sufficiently centralized ancient state and restoring the Republic on a more sustainable foundation probably results in an early Industrial Revolution.  Technology takes off as soon as people see they can benefit from their investment instead of having it all confiscated by an autocratic state, or by bandits if the state is too weak.

Slavery never getting a foothold in the US probably does not change the technological frontier much, but results in the South being as rich and technologically advanced as the North throughout most of US history, in addition to obviously being freer. Also results in more democratic design of federal government. Probably results in earlier elimination of things like malaria and hookworm from the South, and higher GDP per capita and more secure voting rights there today.   More tentatively, makes the US a more appealing model for post-colonial states to design their governments around, so maybe more of them develop separation of powers and end up democratic and prosperous, and fewer ever become communist.

Starting in the 1960s, the neoclassical economists took certain conclusions and assumptions much more seriously. 

Milton Friedman's suggestion of a negative income tax became accepted best practice and led to a small but growing UBI throughout developed world. There was much less pushback against globalization, free trade, or automation, since everyone directly benefited from rising GDP.

Paying more attention to the risks of market failures leads to requirements that all companies buy generalized externality insurance. (This was inspired by Fall of Doc Future mentioning such a thing, but the mechanism I'm proposing is my own off-the-cuff spitballing). You pay an insurance premium, and any time someone can prove that an action you take imposes costs/harms on some group of people or companies, the insurer sets up a fund to pay out claims to them, and your premiums go up. Any time you can prove you are creating a positive externality for another firm, their insurance company pays yours and your premium goes down (or you get a rebate). I suspect this would be too complicated for individuals to carry such insurance, so the government acts as the insurer who pays for positive externalities that accrue to individuals instead of companies. This makes the overall system positive sum for companies that actively and effectively strive to make others' lives better.

By 2010, globally, compared to our world, rGDP per capita was 30% higher, carbon emissions per capita were 50% lower, average hours worked per lifetime were 20% lower (some people have shorter days or four day weeks, some have longer annual vacations, some have mini-retirements between jobs, some take off for 5-10 years to raise children). 

Schools and colleges (first private, then all) are forced to pay for the secondary effects of their own practices on children's mental health, and downstream effects on crime and poverty rates, and not just in their own districts, enabling efficient distribution of funds across geographies to optimize the societal benefits of education. 

Anyone who can prove that companies' practices lead to governments competing to provide corporate welfare forces said companies to pay it all back in premiums, eliminating the practice and letting communities reinvest their tax revenue in themselves instead.

Developing countries successfully obtain compensation for exploitative actions, leading to more humane and sustainable development and further accelerating the trends towards automation, resource efficiency, and dematerialization.

I may be stretching the point about changing human psychology here, but: 

Education is widely considered to include learning how to be a emotionally well-adjusted and responsible adult. Schools teach things like mindfulness and intra-personal conflict resolution. For example, kids learn how to recognise when they are reacting from anger, and therefore how to take a breath and try a more mature reaction. They learn about concepts like how stress can make you start catastrophising, and how to apply some cognitive behavioural therapy to oneself or a friend to head off mental health problems before they get started. All of this is considered as normal and basic as learning how to read: it is assumed that almost any functional adult will have these life skills. 

The consequences for later life are immense and flow through every part of society. A more responsible and well-adjusted population is happier. Workers are more productive (although this may be expressed by the same amount of work being done faster so everyone has more time for the important things in life). Every kind of destructive behaviour is much less likely, whether in mild forms like chronic worrying through to extremes like domestic violence or addiction to hard drugs. People expect political leaders to be sane and reasonable, and will strongly reject those who pander to the worst human tendencies, meaning that most countries are better-run and have wiser policies.

Not a paradise of mine (that I'm researchin'), but here's an utopia with past tech* I thought you might be interested: "Walden II" by Burrhus Skinner, conceive a "small-time" utopia-like fictional effort, inspired by science, without any "alternate history" (in the law-and-politics scale). Just sheer enterprising.

As a genre of fiction, it's quite cool. It inspired quite a few hopeful real-life "utopian communities" as well. Some with stories that can be read online: of both failures and achievements. Some ongoing right now, and can be visited with the proper previous announcement and subsequent consent (people's homes, after all).

If anyone reading this becomes interested in some planning, and would like someone akin to periodically talk to, no bets attached, I can be found online for message exchange.

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*current tech, when written. The passage of real-time and new techs are addressed on a fiction-continuation article, "News from nowhere, 1984" by the author.