Cheering for my national hockey teams, and Canadian UFC fighters, is about as passionately nationalistic as I get. I do get into it for sure. But really, I'm pretty easy, because I just like the competition. My favorite player of all time is Russian. Pavel Bure. I had friend who, and i kid you not, threw his living room furniture onto his front lawn when we lost the 96' World Cup to the U.S. He's mellowed out since then. :)
I was born in the United States, and have dual citizenship, so I've never really been nationalistic, and during the Olympics I usally just root for the underdog.