I am an american so i believe i have a valid viewpoint on the matter.  The Roman Empire went through various phases throughout its duration.  I believe that america can avoid the same fate of the roman empire if it stops intervening in other countries' affairs where there is not a dire need for American Prescence.  If America reverts back to a non-intervention (pre-WWII) foreign policy and stops trying to police the world on its own; then yes...America will fall, maybe not to the degree of the Roman Empire but definitly get knocked down a notch.  But if america can change its ways, strengthen its defense of the homeland and pretty much let the world know that we're not going to be the chapparone anymore; then i believe that the world will realize that they need to work together and find a way that is good for everybody.