I've always found it very interesting how the US Men's team is somewhat mediocre (compared to American performances in other sports especially where the US dominates) while the Women's Team is extremely good and an easy world cup contender.
Certainly an interesting contrast.
In the US, we have a gender equality law called Title 9, which wasn't really intended for sports when passed, but because of that every middle school, high school, and college, spends as much on women's sports as men's sports, developing talent and all that. Because (American) football doesn't really have an equivalent, it means that sports like soccer, tennis, volleyball, etc., end up being a lot better funded on the women's side than the men's.
Granted, the World Cup team has had a whole lot more development than just school and college, but the fact that every single school with sports puts money into things like women's soccer means there's basically no chance that a potential talent slips through the cracks.
Combine that with dead0man's point, that top female athletes are way more likely to focus on soccer than top male athletes, and our high population, and I think you have a good explanation for the disparity between the men's and women's national teams.
In a world where soccer could bring in as much money as (American) football, Odell Beckham might be the top soccer player in the US right now. He was dominant at both sports in high school.