Well, yes every world power has fallen apart, but not all for the same reasons and not in the same ways. I mean look at Genghis Khans empire... With Bows and Arrows he controled the literal world at the time. HIs empire was the biggest in history, and it bassically fell apart with his death, and the advancement of weponry.
The roman empire fell apart becuase they decided to tax people with goods instead of money. So, Each of the provinces being controlled would have something the empire needed. LIke Wheat, fruits, vegies, or weapons, ect... Well, then the food and such dried up, so did the control over the empire. It couldnt sustain its self.
The British Empire in my opinion was the world superpower until the United States created the A-Bomb.
Everything in this world is bassically even. Even in 3rd world countries there are computer technology, McDonalds, paintball, ps3,xbox ect... Its just the availability and frequency of use that changes. The only thing that makes you who you are in this world is Fire Power.
The United States is not the richest country in the world. In fact the last GNP figures i saw, the US was ranked 5th. People consider the US to be the SUper Power becuase of Fear. We like to use the media to our advantage. Showing the world what kinds of new killing toys we have so no one wants to fuck with us.
We have the worlds largest stock pile of Nukes in the world yet we cant use them. The US spends billions of dollars every year of money that it doesnt have to fund Military projects.
Now China is in the Mix, buying up majority stock in our Publicly traded markets. Riseing army in numbers greater than the United States has ever had. The only way for China to take the top spot against the US is when Obama fully plunges us into the 1930's recession x 1,000,000 with all the shit hes pulling.