I think a part of the problem for many (like me and I'm guessing MattMang23) who grew up rooting for Italy in soccer, we were ridiculed for watching soccer in the first place. The game was some "weird European / South American thing", and due to that mentality from most Americans, we never really had a chance to root for the US team or players. They were hardly ever on tv, and they were a running joke. In fact, you were more likely to catch a Mexico game than you were an American game.
After the 1990 World Cup, there was a resurgence of American soccer. More and more people began to respect the sport, and more importantly, the fans of the sport. I may root for the U.S. in the matchup against Italy, unlike MattMang23 who roots for Italy, but I always feel conflicted. The Italian players are more likely to be my "soccer heroes" that I watch every week on Fox Soccer Channel. The only Americans that I can watch on a regular basis are Clint Dempsey and Tim Howard in the English Premiership. I definitely understand the "immigrant kid guilt"...