Why doesn't U.S. soccer seem to have an upper hand when it comes to world soccer? I believe that its simply because other countries don't have access to as many alternate sports as Americans typically do. Therefore, most international athletes are funnelled into soccer or futbol. U.S. athletes are much more diversified when it comes to sports in relation to other countries. There is no doubt that there are many athletes from basketball, baseball, football, and so on that would give much needed help to U.S. soccer - provided a soccer foundation.
I can only imagine that U.S. soccer would be ranked somewhere near the top if its resources were focused more on soccer. However, soccer is much less important to most Americans - it seems - than the other top sports. Think if athletes like Reggie Bush, Ladanian Tomlinson, or Dante Hall took those mad footwork skills to the soccer field? I'm not saying they would certainly be good but I think there would be potential. Additionally, lets look at other masterminds such as Tony Parker, Steve Nash, Chris Paul. I would even give Kobe a shot at goal keeper.
Pound for pound, I think football, soccer, hockey, basketball offer pretty similar physicality with athletes. Baseball sides much more to coordination talent and less to physicality in relation to the other major sports. Football requires a lot of strength relative to the other sports. However, hockey, soccer, and basketball require a great deal of endurance. All require different particular skills that contribute to a great athlete. I don't think a single one offers a better physical athlete than another, though. Mentally, I would say baseball is one of the toughest. Coming through the ranks is always long and trying and there is endless competition with other athletes. Also, because of the way athletes can hit these days, you can never stop practicing and training to be better. Then once you've made it, there's tons of others looking to take your spot. Then there's the 162 game season which puts a cherry on top of that mental toughness category.
A young American athlete would have no reason to opt for soccer if they had a chance at NBA or NFL money. But if we respected soccer the same way others countries do then that would change. If American soccer players knew they could make what Beckham, Ronaldinho, or the Real Madrid players make then I imagine the payroll bias would go away. I imagine with soccer's popularity growing it won't be too long before more American athletes start taking soccer more seriously at younger ages. Then we will see this U.S. team climb the ranks.