Modern prosperity is caused by modern policy. I've seen some reasonable theorising that income basically comes from how easy it is to do business (thinking especially of https://www.grumpy-economist.com/p/the-cost-of-regulation). Which is linked in no small way to the cultural factors chgs pointed out - the most vibrant and high income industry in the world is also the one that sees laws impeding them as a problem that can be overcome.
The attitude of doing things that create wealthy even if NIMBYs object is an attitude that leads to wealth creation. Strange but true. Not the only factor, the political strength of the opposition matters a lot too.
The only thing special is our geography and history. It's really hard to launch an attack unless you're in Canada and Mexico. So the US smartly made treaties and agreeemtns instead of repeating the bloody history Asia and the now EU went through as they constantly battled neighbors.
Only Australia has such a similar advantage and instead they had to war with nature's deadliest critters trying to kill them (they arguably lost).
I mean sure, in the 50s the main driver of prosperity was whether a country had avoided being invaded and that isn't necessarily a result of a country's legal system. But the 50s was a very long time ago now and the era since then has been quite equal-opportunity outside pockets of disaster in Africa and the Middle East. The USSR, Chinese, Euro and US experiences haven't been determined by external factors or historical determinism as much as internal policy choices made in the 60s, 70s, 80s, 90s and 00s with a 20-30 year lag before the decisions start to turn up in real life.
Even if we indulge in wild conspiracy and pretend there is a shadowy cabal in Washington that decided to crush the USSR and exalt China economically, that cabal would have had to implement its decisions by somehow guiding internal policy choices in the respective nations. Nobody has managed to do anything to either of them through external pressure that holds a candle to the internal choices made.
The US in particular benefits from an absurd amount of resources (not least of which is land), a perfectly safe geographic position, the global language and an immigrant culture. Basically able to coattail the British after independence, the destruction of much of Eurasia during WWII cemented its position as first. And great diplomacy, including the Marshal Plan, enabled the US to create an international system with many benefits and natural synergies with its inherent strengths.