That's a book sized topic and I'm probably posting to this thread too much already. Still, go big or go home, right?

The EU enforces a very specific economic and social model which prioritizes geopolitical unification over wealth creation. External tariffs are high, there are many other less obvious protectionist policies in place, regulation is vast/constantly growing, there's a lot of grant dependency and internal subsidies, the EU theoretically doesn't control tax but in practice has taken control of it anyway and now prevents tax competition (see Ireland), and the ex-Soviet states have provided a legal pool of very cheap labor which has systematically discouraged investments in productivity for decades. The Euro creates a whole other set of problems but fortunately the UK avoided that. Because the EU's scope constantly expands this results in the slow strangulation and homogenization of local politics: huge swathes of policy that people care about are effectively off limits and politicians from all parties simply refuse to discuss them at all, knowing that there's nothing they can do or say because the EU will simply overrule them. It was often very unclear to voters why these "black holes" existed or even what they were exactly, because the middle class consensus was that the EU should be beyond criticism and is at any rate an immovable object, the ever-increasing dominance of which was an unavoidable fact of political life best left undiscussed.

The UK's divergence from the USA in wealth terms isn't directly caused by the EU. That's why I say the EU locked in social problems, rather than causing them. The divergence really kicked into gear after WW2. [1]

Post 1945 the USA continued its more explicitly capitalist and libertarian approach, wheres the UK became wedded to the European social model. Compare employment law between Europe and California, recall all the usual HN discussions about why Europe doesn't create tech startups at the same rates, etc. It's all a part of the same package of attitudes that creates those outcomes. Inside the EU divergence from this model towards something more explicitly pro-business is simply not possible, as the Irish have discovered. They were picking up US tech firms and investments like candy due to their low tax model, but the EU preferred to forcibly align everyone on French levels of corporation tax to avoid "harmful tax competition" [2]. It doesn't even control such taxes by treaty, but treaties are largely irrelevant in Europe - the subservience of the political class and fear of EU retaliation means there are no real checks on its power, and thus they were able to bring Ireland to heel anyway.

Outside of the EU the UK can in theory diverge from this approach and pursue a more US style model, eventually perhaps even catching up with US levels of wealth. Certainly that was a big part of the appeal to a lot of the Brexit campaigners. However it isn't on track to do so currently. The social attitudes described above have been a feature of British society for many decades and the Conservatives are effectively a centre-left party dominated by the need for wealth transfers towards the the pensioner demographic that reliably turns out to vote for them. Even if alternative parties appear, alternative social models start to be discussed and attitudes change, it will take a long time to even re-match the USA in terms of growth, let alone close the gap. That's why I think the impact of Brexit will have to assessed by historians over a span of a century or more, in the same way people still debate the impact of the events of the 1920s today.

So - it creates new options. People haven't even been thinking about those options for nearly 100 years, so nothing is going to happen overnight and it may never happen. But at least it will mostly depend on what voters want.

[1] https://ourworldindata.org/grapher/maddison-data-gdp-per-cap...

[2] https://taxation-customs.ec.europa.eu/harmful-tax-competitio...