Is it possible the U.S. will be defeated? Shure it is. Today we are the big kid on the block and nobody can even come close to our combination of high technology, economic power and political might. But when a person or a nation becomes overly confident that's when your in trouble. There are many scenarios that you can come up with such as China, India and Japan joining forces in some kind alliance to defeat the west, but like has been said already in response to this question, why would such a thing happen when our world is truely becoming a global villiage. We are connected to each other so much economically the major contries of this world need each other in order to prosper. Sure the U.S. may fall some day but if it does it will more than likely be a long slow evolution into something different than it is today, and by then the same could be said for many other nations as well. As odd as it may sound, 50, 100, 150 years from now the threat may be from a united and powerful Islamic Africa, were many poor, ignored, disinfranchized black nations, feed up of being ignored by the rest of the world may become educated and powerful enough as a union to be a real and viable threat. Impossible you say, look at the political and military history of the world. Nations rose and Nations fell. Never say never. Wrap your mind around that idea....