I love Football (American Football). It's the team spirit of things, and Football is the ultimate team sport. I rep my professional home team (Washington Redskins), season ticket-holder, all that business. If you watch enough Football, and start to understand the games, you can see how well the good teams flow like water, and the rest choke on key parts. I know I'm likely not going to convince you to watch, but I strongly suggest it. Insane things can happen (The Immaculate Reception)
On your point of loyalty and team-swapping, that's a lot more common nowadays than in the past. Previously, a player was drafted and pretty much stuck with that team until they retired.