The problem is pretty simple, one administration borrows a bunch of money to try and give the voters what they promised during their campagins in order to keep getting votes. Then the next administrations goes and issues even more debt in order to do the exact same thing. There is no incentive to be smart about moeny when you get into power by spending money you don't have. The thing is that currently 40% of eligible voters don't pay taxes, it only a decade or two away that we will have greater then 50% of people who don't pay taxes voting. At that point they can vote whatever insane taxes on the working class they want and force us all to pay for their idiocy. I'd imagine at that point we will have some sort of radical revolution. I don't think anyone can stop the comming depression, just hope that it doesn't result in war.
OF course, China really isn't any better off. Their own revolution is coming too as all the people there decide they don't like being the governments bitch. And I'm sure when the US goes down and they have nobody to sell all their useless crap too that they will be drug down with us. Again, I just hope nuclear war is not the result. Throughout history if you lok at times of peace, or the time that a country normally sits atop the world it seems that 50 years is about average. We are already past due since winning WWII and I really dobut we will make it another 50 years that I will remain alive (God willing).