I think there is more to it. The USA has well the U and S - a homogenous enough and high population bunch of wealthy (relatively) English speaking states with s

I think there is more to it. The USA has well the U and S - a homogenous enough and high population bunch of wealthy (relatively) English speaking states with similar enough laws/rules when it comes to commerce that you immediately have a large incubate market before your product can go global. This probably network effects into more funding, which creates a feedback loop, centered on the schilling point of Silicon Valley / SF etc. If I needed a $1m for an idea, I can go beg for it in Australia, UK etc. have the Dragons Den types laugh at me for not giving them 99% for $100k, or I go to the US and have a different problem - how to choose which investors to dedicate my time to, and which are wasting my time. But getting the money is not the problem.