There's a 10-year-old book that predicts an eventual breakdown into smaller, more independent entities, citing the bureaucratic and monetary incompetence and despotism that is inevitable in any empire. The authors suggest that the information age will eventually usher in that change, and it's interesting that the current growth in anti-establishment sentiment (e.g., "tea parties," the Ron Paul campaign, secessionist organizations, etc.) has been largely enabled by the Internet.

The founding documents of what has become the U.S. contain the very seeds of its own destruction:

"Governments derive their just powers from the consent of the governed... it is the right of the people to alter or to abolish [bad govt]... it is their duty, to throw off such government..." — Declaration of Independence

And the constitutions of many states contain similar language.