Didn't read the post, but the problem is that in most top soccer countries, soccer is the number one sport, light-years ahead of everything else. In the US, several other sports are more popular, which drains the talent pool. Kids grow up immersed in soccer culture in places like Brazil, Argentina, Germany or Spain in a way that simply isn't as common in the US.
I think that is a contributor to the problem but the real problem is we do not yet know how to develop talent consistently in the US. FC Barcelona is easily the world reference recruiting kids around 7-8 years old and building them mentally, physically and tactically into incredible players. Something like half or more of their current roster came through la masía at some point. And something like half the Spain world cup roster plays for Barcelona.
There are soccer academies in the US but it is still relatively new and we do not have a great development model yet. Youth academies are also fairly antithetical to how talent pipelines work for the established US sports.
I get this argument, and it is probably partially right, but is soccer really competing for the same athletes as basketball and American football? Basketball players are mostly too tall for soccer (other than goalie), and a majority of football players are way bigger than great soccer players. Baseball and hockey might compete for the same athletes, but a huge percentage of baseball and hockey players also come from other countries.