To start, I live in Virginia Beach and have been here most of my life. My mom is British and was raised partly in England and partly in Germany(where I was born). We lived in Italy a few years as well, but I've mostly grown up here in VA Beach, where there's really no 'home team' of any sort.
New England Patriots - my dad was from Boston and was a big football fan(played in high school), so ever since I was a kid, I was cheering for the Patriots, which used to be a painful experience. Its been nice to see them rise to power and objectively, they have one of the most exciting offenses to watch, so I have no qualms about being a Pats fan, no matter how much they're hated now.
Scuderia Ferrari - Formula One is my passion and I started watching casually around 2005. Ferrari's were(and still are) my favorite road cars, so I chose to support them at the time. They weren't very good in 2005, but I soon discovered their racing history and saw what they were capable of in the next few years. I like that the team is the only one thats been around since the beginning of F1, and even before that, the only reason they ever started making road cars was to fund their racing program. They're a very passionate team and I enjoy that.
I've still yet to pick a team to support in soccer. I dont watch MLS, only European teams and international competitions. I'm leaning towards Bayern Munich at the moment, but I've also really enjoyed watching Barcelona's slick passing and Messi of course. I dont want to just pick the 'best' team, though. Bayern Munich is an exciting, relentless team to watch and are from my country of birth, which is a plus I guess. I dont know if they'll be 'my' team in the future, but I'm definitely rooting for them in the Champions League at the moment. I dont like Ronaldo, so Real Madrid is out of the question at the moment. Also followed Everton for a little while when Landon Donovan was there along with Tim Howard.
Most other sports I watch, particularly different racing series, I generally follow individual players/drivers/riders.