"Not being bombed back to the stone age" in WWII gave the USA a huge comparative advantage. Everywhere else got completely trashed and the USA ended up with 50% of world GDP in 1945. So that might be an impressive statistic, but you've slid all the way down the ranks ever since the end of WWII, not climbed up. Going into debt by $18 trillion helped too (in the short term).
USA is the third most populous country in the world btw, after China and India. So to say "we're huge but we got this covered" isn't really saying a lot because there's no-one else in your size class that's a good comparison. Also GDP(PPP) per capita doesn't take into account how income is divided up. It could be one guy with all the money and a teeming mass of penniless people, so it's not a great measure of how a country has flourished for it's regular people.
Here's a better measure, look at
median adult wealth, which is how much assets they typical person manages to accumulate in their lifetime. This allows you to get a good picture of how everything stacks up in the long run - wages, cost of liviing, taxation etc. If the common people can accumulate wealth, you can say the overall system is working pretty good:
https://en.wikipedia.org/wiki/List_of_countries_by_wealth_per_adultIn America the net
mean wealth is $300,000 whereas the net
median wealth is $44,000. Some countries have both a high mean wealth and a high median wealth, meaning that the wealth has spread from the rich to the middle class. That hasn't really happened in the USA.
Australia has a net median wealth of $220,000, Japan has a net median wealth of $110,000, Italy has a net median wealth of $138,000, and
Canada has a net median wealth of $90,000. That's what having an actual middle class is like.