The U.S. definitely has a massive amount of geographical advantages, but I like to use Russia as an example when considering if that's the ultimate determining factor. Look at the way that state is floundering despite its massive advantages. System of governance and culture can counteract nearly any tailwind, in my opinion.

Also, it's true what you say about population density being very different between the two countries, but I don't know if it's fair to act like the U.S. would implode if it had increased population density. I mean, New York has a much higher population density than Tokyo, for example, and NY is a storied and highly accomplished city, despite its warts.