Athletic American men can probably make more money playing another sport. You get perks like (mostly) free college. Paths to the pros are less uniform than the college -> pro pipeline, so even when the US has a generation of 11+ world class players, because they've been trained differently and play much further away from home, they can't come together with just a few weeks of training as easily as, say, a basketball team. Plus, the local competition isn't very good. It's just other middling teams and tiny countries.

Conversely, the NWSL is likely the most lucrative league for women besides the WNBA. In both cases, it's a legit pipeline from college to the pros. Women's hockey is similar. So you have a group of players who know each other, have been playing together for a while and were roughly trained the same way. Also, the second best women's soccer team happens to be in their "division".

They can come together as a team better than American men who all went through different training programs from youth.