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?)

<Inst#cspell>
An empire is a political entity held together by sheer political or military will. A nation state is a political entity that is held together by the cultural or ethnic unity of the population.

No, the United States is not an empire, because if you toppled the government, Arkansas and New York would not secede from the union.

More importantly, is Canada an empire?