The simple fact is most Americans do not understand football. They harp on about the "athletes" and "athleticism" but the reality is football has nothing to do with athleticism, its a game of skill and tactics. Also the tallent pool is far deeper than any american sport so you have to develop your skills from birth, its not like American Football where you can just get roided up and throw a ball about.
There is so much specialization in NFL and basketball that people start to believe these are the 'best athletes'. Look at Steph Curry. Is he the best athlete in the NBA? Of course not! Tom Brady, the best athlete in the NFL? Not by a mile!
Basketball favors tall, skinny, fast players, with long arms. Football favors size and strength, with explosiveness an added bonus. Soccer, well, it doesn't really matter how tall, fast, big you are if you can't run for 90 minutes, does it? And running for 90 minutes in a soccer game is very different from running around a track for 90 minutes. And if you are big, fast and tall, and can run for 90 minutes, can you kick a ball? Even then you have a long way to go before you can play soccer at a decent level.
Former NFL players, linesmen, are dying before the age of 50! My God, the fitness, the athleticism!
America is literally stuck in a 1960s mentality, when it comes to soccer. That was about when the rest of the world realized that you want to turn your best soccer players into better athletes, not your best athletes into better soccer players (an important distinction).
It reminds me of the movie Armageddon, where they decided it was easier to teach oil rig workers to become astronauts, than teaching astronauts how to work an oil rig!