Actually most Americans don't know that. They have no exposure to it. When they see a piece about it on the news it is literally treated as some throw away story. Literally as if it is just that game the Brits like. That's how it is represented in American media. That is it's full attention.
Most Americans think the latter. They dont think much of Soccer but everyone is aware of, in particular, the impact football has had on Brazil. Hell they even made a Simpsons episode about it. You might not know much about it, but I've been to America aswell and they play a lot of English football on TV. Even as far up as Jay Z are big premiership fans. You might not watch it, and the majority of people won't talk about it (in the same way I wouldnt talk about basketball), but it's still a very big sport in America, shown by investments put into LA Galaxy and NY Red Bulls.