I like watching baseball but don't really have a team. The Cardinals if you had to push me, just because I was a rams fan when they were in St Louis. I've seen a Mets game live and been to Fenway Park as well so have soft spots for those teams too.
I don't get basketball at all. Does nothing for me.
I like a bunch of college football teams but I'm not a fan of any. I mostly just want alabama, notre dame and ohio state to lose. I love watching college football nearly as much as I love watching the NFL though. It's brilliant.
Don't know enough about ice hockey. I think I'd enjoy it but I can never follow the puck on TV. Seems a better in person experience to me.
In terms of non-US sports, I am most likely the only Ross County fan any of you have ever come across, if you've even heard of the team. I like Stuttgart in the German league and I watch loads of the Premier League without really having a team. Obviously anything Scotland are playing at. I really do not like any of the English national teams and very much enjoy when they lose. I hate the fucking Welsh even more though.