Remember you have to normalize for population size. And when we say the US we really mean one small part of it. People in the US often move to California to start their startups, they don't necessarily stick around in the part of the US they're currently in. This is largely due to the VC ecosystem there which makes "irrationality" relatively safe vs everywhere else in the world where it doesn't. Tom's article makes this crystal clear when he says:
> The downside of early-stage investing is that you lose 1x your money - it’s genuinely not worth worrying much about
The only potential downside is only losing all your money, what kind of stick in the mud would care about that?
So anyway, we might ask why is the VC ecosystem so much stronger in California than in the UK. But a lot people don't like to think about that because the answer is so obvious: in the 70s when Silicon Valley was getting established and the flywheel of founder->startup->success->sale->VC->founder was spinning up, the UK was mired in socialist hell with rotating power outages, militant unions toppling governments, four-day working weeks and an IMF bailout. At that time making a startup was entirely pointless and a VC fund literally impossible, because the top tax rate on investment gains peaked at 98%. You could invest in startups but the deal presented by Labour was: if you lose money you lose it, if you gain money you still lose it.
Thatcher and then Major beat back some of the most extreme aspects of this, and in this period the top level tax rates were systematically reduced to more normal rates. But Britain of the 1980s was still drastically more investor-hostile than the USA and there was no venture culture as a consequence. In particular the practice of granting equity in startups was not really known (notable exception: ARM, one of the few successful tech startups the UK has ever produced).
Even today British governments routinely levy so-called "windfall taxes" to grab the profits from companies that are doing well, the moment they have an opportunity to do so politically. That culture gap is ultimately the major difference. The idea of a windfall tax in the USA is hard to imagine, I'm not sure it's ever happened.