Nope, this is not about the Patriots Team, but a more general query.

I can understand when one national team is playing another, such as at the olympics etc then people would stand and do the whole national anthem thing for their respective team.
However, is nobody else completely freaked out that this concept of national anthem before every sporting event, even a local team playing another local team, is completely and utterly nuts?
What exactly is the point? They are all from the same country. It just makes absolutely NO sense whatsoever. I think this is only seen in the USA. 
Can someone with a logical reason please explain the link between sports and nationalism?