To me the argument that our best athletes play football, basketball, baseball, hockey, or maybe golf is over simplified. My kids' high school is a good example. The football team is of course top dog. They even have a very good basketball team that has put a few guys into Divison 1 colleges. The baseball team is solid as well and puts players into Division 1 colleges. The golf team the same. Even the lacrosse team has put a couple of kids into college. it's the US south. Athletics are big and football is king.
Even in that environment, the soccer team is something special. They are routinely ranked nationally for the winter season and have several state titles. This is in an area with little soccer history. There are plenty of kids between 6 foot and 6 foot three or 6 foot four who don't have great outside shooting and don't have the bulk to be power forwards or linebackers. A few can be receivers but many lack the hands for that or the willingness to get blasted as only a football player can. In some cases the parents won't let a kid play football here. I don't blame them, it's pretty brutal.
I have to believe around the US there are plenty of very good athletes not quite dense and heavy enough to be linebackers or not quite fast enough to be point guards, can't hit a curve, etc. Let's face it, soccer is a unique skill set. Run tirelessly for 90+ minutes and have amazing footwork. Someone who fits that bill isn't necessarily suited for the other sports. Just my thoughts. I'm sure some of the US soccer hierarchy have pondered this very same issue and so far there are no obvious answers.