What is a metaphor that describes the United States? ANy ideas?

Question

I need some examples of a metaphor that I can use in class....every one is to give one..

Answer 1

America is Rome.

Answer 2

actually its the salad bowl now- we don't mix, we mingle. :P

Answer 3

"The Melting Pot"? Can't go wrong with the classics.

Edit: Is it? d**n, even our metaphors have to be healthy.