Interesting stuff.
Baseball:
Perhaps baseball has something. In Mexico City, there were two teams, the Tigers and the Red Devils, every series they played was called "the civil war". Yet nothing at all happened at the stadium. Devils followers sat from home to first base and right field; Tigers followers, from home to third base and left field. No fights ever erupted. In fact if a big group of friends went to the game, some of them "tigristas" and some of them "diablistas", they would seat in the side of the majority.
Now the Tigers have left the city and I feel so lonely

I've seen on TV that in the US cops enter and easily expell fans from the stadium. A fan grabs a catchable ball (and I'm not talking about the Cubs in the American Championship Series) a cop comes to get him, and he walks out like a sheep. This is unthinkable elsewhere, unless there is a riot going on.
Barras bravas:
I see, from MyOwnUsername's posts that the fame of Argentina's barras bravas has crossed the Atlantic. They have replaced the English Hooligans. The terrible thing about them is that most of them are financed by the teams themselves. Idiotic.
Mexico is still a place in which you can go watch a "classic" game with small children. The hated América Club organized it's "barra brava", but had to dismantle it after the riots against Brazil's Sao Caetano in the Libertadores Cup.
Partizan:
It may sound odd, but Partizan was a very popular team in Mexico, during the late 60s early 70s. The Yugoslavs came to play an "hexagonal" (usually, clubs from South America and Socialist European countries were invited to play against Mexicans), and they had a charismatic player, Hazanagic Mustafah. Once he missed a goal, jumped to the upper goal post and started to do push ups, until the wooden pole broke.
When I went to Belgrade in 1974, the Yugoslav friends (some Serbs, a few Croats, one Macedonian) asked us who were the popular Yugoslavs in Mexico. The answer was easy: Number 1 Hazanagic; Number 2 Milutinovic Bora. Ah, yes, and some people knew there was a Josip Broz, "Tito".
The Germans:
Germany plays everywhere the role of the sporting powerhouse. So, more often than not, the rest of the world wants to see the Teutonic Machine bite the dust (Croatia 3, Germany 0; in France, por example).
I remember seeing the final World Cup game of 1974 in a shabby hotel in Athens. Everyone, but the German tourists, was rooting for the Clockwork Orange. And I mean everyone, from the Greek clerks, to the Gambian students to the Swedish couple.
I root for Germany only if it faces a greater "evil": the US in most Olympic sports, Cuba in boxing, England in football... and, yes, I must admit, I like them to win when one of their players is on my Fantasy League team (Ballack game me some points in 2002

... I may prefer the underdogs, but I don't mind winning

)