Tribalism is found in all levels of human society, but religion, followed by nationalism or the more euphemistic term patriotism, are doubtless the most dangerous and threaten the very survival of our species. There are many things of merit in the USA but one thing that is very dangerous is the wedding of ancient mythology (Christianity) with modern ideas of national identity. The concoction one has after those ingredients are mixed is deadly.
I agree with you about religion. However, being an American, I'm gonna stick with nationalism. Here's why... the world has limited resources, and is overpopulated relative to those resources. Against this backdrop, the world is divided between "haves" (the west) and "have nots" (the developing world), and the difference in quality of life between these two groups is enormous. Since my "tribe" is one of the "haves", I think I'll do whatever is necessary to make sure it stays that way, since as my "tribe" goes, so go I.