Gooooooooooooaaaaal!

I am watching the USA vs. England futbol (i.e. soccer) game. The score is 1 to 1. I must confess both that a.) I really am not a huge soccer fan, and b.) that the broadcast I am watching is in Spanish, so the only words I really understand are: Goal (pronounced gooooooooooooooooaaaaaaaaal!), shoe, and ball. Surprisingly that's pretty much all you need to get the gist of what is being said.
Anyway, like I said, I am not much of a fan of futbol, but like most sports, I can certainly appreciate the skill and physical conditioning required to compete in such a venue.
I find myself shouting "Go USA!" and clapping when my country scores. I feel like I am a part of something, and I feel proud (in a childish, fuzzy sort of way) of my country and the players on the team.
Why do I feel that way? In my reading I have come across a lot of theories on why humans have developed certain traits. Nationalism is a modern form of the very ancient practice of social groupings which are very deeply embedded in our brains. Groups are important because they provide protection for individually weak animals, and they provide a stability that allows several species (including our own) to reproduce and care for young that are essentially helpless. There is almost nothing, besides maybe familial relationships that are more successful in binding a group of individuals together than a common enemy.
As we all know, if you spend too much time in a group, conflicts and problems arise. People get on your nerves, you have disagreements etc. But some species depend on their group in order to survive. If the group is gone, so are they and their genes. Therefor there needs to be a mechanism that stops groups from breaking apart....and that may be where our deep feelings of nationalism and "team spirit" come from.
"I may be saying "Go USA!" But maybe what I really mean is "It makes me feel good to see members of my species fighting (i.e. playing) on behalf of myself and our mutual group which in turn provides safety, continuity and opportunity to me as an individual!"
Well...whatever. GO USA:)