That's not even the worst of it.
I went to an NFL game and the fans were constantly being prompted what to do. The fans saying "De-fence" weren't saying that on their own. We all know about the cheerleaders, who at least started as a group of people who were there to lead cheers. But, these days they mostly just put on short, entertaining dance / gymnastics shows during the periods when nothing much is happening in the game. But, the real "cheer leaders" these days are the screens. There are immense screens in the stadium that tell the fans when to chant "De-fence". Or "Make some noize" (with the mis-spelling of noise on purpose). Or, there was a constant honking from the kind of horn you'd expect on a cargo ship when the other team had the ball and were in a huddle. It's not even the fans trying to disrupt things at that point, it's some guy in the stadium, employed by the home team whose job it is to sound that fog horn.
Now, a lot of that is probably because it's gridiron football and there is more down-time than there is actual time in play. If fans were not constantly prompted to cheer or boo or "make some noize" they'd probably be chatting with their neighbours. That's what tends to happen with slow-paced games in Britain (and elsewhere) like cricket.
As for soccer / football / futbol, in the UK they do really sing about things like someone's drunk driving charge, or someone cheating on their wife with another player's wife, and fun things like that. But, not Debussy's Clair de Lune. What's interesting is that there are so few tunes that are actually used for chants. The oldest, most established ones are based on church hymns because everybody knew those from hearing them in church every week. These days even though people don't go to church much, those tunes are well established for chants. There are also pop songs from the 1950s (That's Amore), 1960s (Hey Jude, Yellow Submarine), 1970s (Go West), 1980s (Just Can't Get Enough), but it's rare to hear a song that's less than 40 years old being used for a chant. Something has to be so well known by fans of all ages for it to actually work as a chant.