Do you really believe that lack of resources in S America meant lack of prosperity? It's still composed of third world countries.
> and may be the least important
It's the only common thread. I provided numerous examples that refute the requirements you listed.
> Japan
Japan's pre-war industrial economy was not an economic powerhouse. Their soldiers were very lightly equipped. They built a handful of capital ships, and when those where sunk they couldn't be replaced. Curtis LeMay resorted to area bombing of Japan because their heavy industry was a collection of homes with drill presses (LeMays' characterization) so there weren't concentrated industrial targets.
What's the excuse for S Korea, Taiwan, Hong Kong?
Have you noticed that when China gave up on collectivism and turned to free markets, suddenly they became a very prosperous world power?
Yes, people preferred to immigrate to the US. Why would that be? Because it is free market and hence a land of opportunity, unlike any place else at the time.
China has an enormous population, but did not become prosperous until, again, free markets.