Maybe, but when I look at the world's best soccer players, they usually don't have NFL or NBA bodies. As with every other sport, being big and fast helps but soccer has its own skill set. It's not athleticism we lack relative to the top countries, it's skill. Maybe a few of the NFL types would have developed it, who knows.
The coaching issue is a fair one, but I suspect the real issue is training, or lack thereof. A kid isn't going to be elite if he goes to practice and then doesn't touch a ball until the next practice. There aren't a lot of gym-rat kids in suburbia, which is where most youth soccer occurs.