I'm not part of the "America is an empire crowd." But I do believe that Niall Ferguson's opinion in the LA Times on the rise and fall of powers is a good read.
America, the fragile empire
PERHAPS THE FACT THAT WE HAVE SEEN MILLIONS VOTING THEMSELVES INTO COMPLETE DEPENDENCE ON A TYRANT HAS MADE OUR GENERATION UNDERSTAND THAT TO CHOOSE ONE'S GOVERNMENT IS NOT NECESSARILY TO SECURE FREEDOM. - FRIEDRICH AUGUST VON HAYEK