Yes, the US will fall, but not spectacularily so. I see it breaking up and fragmenting into a few "super-states" divided along cultural and racial lines. China and India cannot even provide clean water to a large segment of its population and cannot feed its massive population either due to poor agriculture. These two countries depend on food imports to survive. Europe? Doubtful, with a mix of socialism and a burgeoning Muslim population that is hostile to the natives there.
What no one has mentioned yet is that there is a glaring similarity that is shared by the Roman, Byzantine, and Spanish empires when they fell......they all deviated from the gold standard and began to debase their currencies in favor fiat money and coin clipping. The Roman Gold Aureaus and the Byzantine Gold Solidus were heavily traded and held high value long after those empires ceased to exist. And look what we have here in the UNited States...a complete fiat money system, skyrocketing gold spot prices, inflation, and severe debt.
Additionally, one must look at the racial and cultural makeup of American society. In reality, we are really only held together by the glue that is our economy. Our standards of living are very much beyond than those of others throughout the word. Honestly, who would have the time and inclination to hate or fight someone who differs from them when there is an SUV and mortgage to be paid, and Monday Night Football is on? We've already caught glimpses of how vastly different we really are in regards to each other and these events only enhance that view....Hurricane Katrina, the 1992 Los Angeles riots, the current illegal immigration debate, the rise and power of race-based special interest groups, etc...
Now, look at what happened near the end of the Roman Empire. The diversity of its national, ethnic composition began as a strength but later aided in its failure; the Barbarians entered into the kingdom peacefully laying the foundations for a multicultural society, but later turned against the Empire by capturing provinces in an attempt to segregate and establish distinctive boundary divisions, i.e., a kingdom within a kingdom. Do we not see the exact same thing happening in our American Southwest? These are not just low-level gang members and uneducated unaware Mexican and Central American immigrants declaring this land is theirs.....it is also privy to the highly educated and powerful such as mayors and interest groups such as La Raza stating this very thing.
This is definately a very long and involved discussion to get into, but interesting nonetheless.