2 North American 4 You

Once you have a class of people, who don't need to work, they will do interesting things. Many scientific advances and exploration was done by nobility and rich, who could afford to do something with their lives, which didn't directly make money.

It's easier and less risky to try to become a pro athlete, if you have enough money so you don't fall hard, if you fail.

However for sports, there's also huge programs run by states. Socialist countries typically put quite a lot of resources into identifying talent early and then systematically training them. The Soviet Union and later Russia are especially known for this. Many militaries allow soldiers to become full time athletes while being paid as soldiers. This works really well for national prestige.

America got rich because when the rest of the Allies were fighting the Nazis they sat back and loaned resources

America was already rich before WW2 started. During WW2 nothing in the USA was destroyed by the war, whereas Europe was devastated.