I feel like the idea of America's exceptionalism is inextricable for many people, largely conservatives, from patriotism. It's not
really about America being objectively the best, it's about pride in your country. It's just rooting for your team. "Seahawks are the best!" "America is an exceptional nation!" You see it less with liberals, because for many reasons we reject what we think of as jingoism.
Then again, its not just politics that influences these things. I'm from a family of Atlanta Falcons fans, so my own team-rooting has always been more...cautiously optimistic.