Simple, you cheer for the country that's playing against a country you hate, it's not that hard.

Now listen here bucko Japanafornia's great, yes the in world explanation as to why there's so much Japanese stuff in there is down right Utopic but it's fun and that's all that matters!
N' besides could you really live with yourself if you knowingly deprived generations of gamers all those beautiful pun names!?