Although it should be said the economic success of the Americans hitherto is also quite foreign to the rest of the world; and driven mainly by their legal quirks.
That seems rather focused on one policy that was big in the 50s. The Marshal Plan was great but that isn't something the modern US seems to be capable of - since around Vietnam I think was the change. It has been a good 50 years where the US just breaks stuff and leaves it broken.
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 book Why Nations Fail makes a pretty strong argument for the core feature of successful societies to be strong institutions with low perceived corruption. Sensible laws that are upheld equally are a part of that.
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.
Legalities don't drive profits. If anything the US was simply lucky in thr 50s to not be war torn and rebuilding it's cities post war.
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'm a bit stumped that you don't consider treaties and agreements to be legalities.
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.
