The reason you may not see the best athletes on the US National Team are 1) The politics of soccer in the US, 2) Some of the best athletes who play soccer as their "preferred" sport are multi-sport athletes who ultimately pursue the sport that has a more viable/lucrative career path and 3) A lot of great athletes who play/love soccer are smart and switch focus to academics in college to have a great career outside of sports.
I've mentioned this before, but on my HS team we had 2 players who ran track on the US Olympic team. Obviously, they chose to run track in college. At ND you can look at Shane Walton. He was a Freshman AA on the soccer team before switching to football his sophomore year.
In any event, you are correct in saying that the US National team doesn't get all of the best athletes in the country. However, you could tour the top Club teams and find players that are twice the athletes as the ones on the National team.