It's not population. Yes, everyone will point at population, but it's not population that's the explanation. People imagine that you have to have a bunch of talents born, so the more people, the more talent.

Phenomena that are largely uniform are explained by population. Why does American have more women than France? Well, the generation rate is more or less the same, so the bigger country has more.

Iceland with 400K people managed to knock out England, population ~60M, from the 2016 European championships. China played in one world cup and has struggled to qualify for decades with 1.4B people.

Being good at soccer is not uniform, because the generation mechanism is not the same. Countries get good at soccer when they have good systems for developing talent, ie making the talent, not waiting for it.

In the US, you have some special factors:

- Pay to play. They turned kids soccer into a consumption good, which you have to pay for. In Europe, if you are any good, you play.

- Competing sports. If you're athletic, there are similar games you can play, with a much more developed youth system, particularly where you can get yourself a degree for free. The systems to develop you into an NFL or NBA player are there already, everything from recruitment to NIL deals. To do soccer, you need to find a way to get in front of a European recruiter.

- College soccer is not a pipeline into the big clubs in Europe. In Europe, the kids have already been selected at age 10, and the good ones generally don't go to university.

On the women's side, this is different. US Women get an advantage from the college system, since professional women's leagues are a relatively new phenomenon. They are guaranteed some funds to play in college under title IX, so effectively they've got a massive league subsidised by the universities. As the rest of the world has gotten serious about women's football, the US has been less dominant.