For those who predict Iraq war is the one ending U.S. empire, well, you may draw your conclusion too earlier and too fast.
After Vietnam war, U.S. perspective was far worse as well. A global oil crisis, a way unpopular war in vietnam, much unpopular compared to the Iraq war, a ever-strong soviet empire, bad economy inside U.S., and etc... However, within 15 years, communist-bloc all collapsed.
Today, there is not a single power that can represent then's soviet empire, there is no global oil crisis with U.S. in full control, I really do not see U.S. is really in that bad situation. Even though it is in heavy debt, U.S. still have many mechanisms to deal with it. With Europe in trouble, I do not see where you can draw the conclusion U.S. is near the end.
Sorry to disappoint you even though I am not those who will support U.S. no matter it is right or wrong type of person.