Blowback, by Chalmers Johnson, is a book that talks about America's sort of Empire and the Empire's likely costs. The book's conclusion, that America's dominance and power is fragile is insightful and very pertinent, given the disastrous Iraq war and the drastic decline of the dollar over the past year.

Chalmers Johnson was a former professor of Political Science at UC Berkeley who has just written a new book called The Sorrows of Empire and has recently been getting some press and interviews (more)
Cam Riley: South Sea Republic. Freedom, liberty, equity and an Australian Republic.