I think you guys are mixing up the words "athlete" and "athleticism" (these don't always go together). To say athleticism isn't as important in soccer as in football may be accurate, but that IS NOT a counter-argument to: If the best athletes in the US chose to play soccer professionally instead of other sports, the US would produce top class soccer players.
The US produces a wealth of youth soccer talent, but one thing (more than anything else) keeps us from producing top senior level talent: MONEY. Young athletes in the US know they can get rich playing baseball or football, but few kids who play soccer in the US know this (trust me, even if we here do, those kids in the inner cities generally don't - they don't see these stars on television, in the press, etc...)
So, our best athletes (this DOESN'T mean the most athletic) choose the sports where they see the most money being made. Some things seem to have changed after MLS, but nowhere near where it could be. How else do you explain the composition of the US team? In 1998, most of our players were from white middle-class families!! Today, about half are. After MLS, we see more blacks (Beasely, Onyewu, Pope, etc..) and occasional transplants from other sports (Bocanegra), but where are the Hispanics (Reyna came from outside US soccer, so only Mastroeni - another Argentinian - is the only example)??? And where are the inner-city blacks???
So, it's very likely that if our best athletes (remember this does NOT mean most athletic) chose soccer, we would be a Brazil of this sport. If you think otherwise, you're arguing something in the genetic pool of Americans could never produce top-class soccer talent (and that argument is laughable).