Is America fighting for its empire?

Today my Archaeology teacher was talking about how every empire eventually completely caves in upon itself in one form or another, and I began to entertain the possibility that through all the protesting, arguing, and disagreement- perhaps the United States is acting accordingly.

If you consider what it will be like reading about the US 200 years from now, will its fall be that big of a surprise? The writing has been all over the wall since the 50s, and has riddled major media since the 80s.

So; is America justified in its actions to defend the empire, even if they don't come to truthful terms with them (has anyone ever?)

What in the hell is wrong with you people that don't like this country? Where else in the world can you achieve the sort of things that you can achieve here by honestly working your ass off? Is it wealth envy? Does looking at other peoples' achievements hurt your self-esteem because you haven't done shit with your life? Go ahead, blame it on all the evil corporations that make your life as easy here as it is, and just let the big-government types keep stealing your hard-earned tax payer money to fund things like high-school football teams and the Paper Industry Hall of Fame, and million-dollar bridges to nowhere in Alaska...