Soccer and sports in general are the spaces reserved for tribal and pre-civilized behaviours: rooting for one team against another, chanting, cheering for a victory or for the defeat of the opponent (in confrontations that are purely symbolic). Those who take this behaviour outside of the stadium often tend to salute their comrades with a straight arm, and resort to knives and sticks to prove their superiority outside of the pitch.

Or, you could see it like this. Europe has seen enough of nationalistic pride and of masses chanting in the streets. It didn't end well, and we know it. The USA don't happen to have made the experience yet in first person, though they certainly have a second hand knowledge of it.

Pride in the accomplishments of your own nation is a good thing. However often it clouds your perception of its faults and wrongdoings.

> Those who take this behaviour outside of the stadium often tend to salute their comrades with a straight arm, and resort to knives and sticks to prove their superiority outside of the pitch.

Or... they launch rockets into space, and land them back on a small platform.