What does America need from the rest of the world?
Oil, food, electronics, automobiles, raw materials not found on the North American Continent..
And capital, we don't have the money for either the Iraq war or the bailouts, we are borrowing almost all of it from China. China won't start a war with the US, as if things really go to shit, we can nuke the hell out of them, not to mention we pretty much power their entire economy.
The threat of a WWIII comes from the Russia/Georgia situation, because if Russia starts using an expansionist policy to try and counter the effects of globalization (which thanks to some incredibly corrupt officials has screwed them over royally) everybody suddenly feels the need to start shitting their pants as they still have a shitload of weapons stored up. Que the resumption of the cold war, and the CIA taking down a lot of socialist governments that have popped up lately, especially in South America.
As for us participating in WWIII, when scared people are given an enemy, they are become far easier to control, and with massive production starting to take place as we arm ourselves, it could be good for the economy. But you know... fucking MAD, we all go down together.
I strongly doubt that short selling is the root cause of the crash. Short selling only causes changes in the market through influencing the psychology of other traders: if they see a lot of shorts on something, they will avoid the stock because they think it goes down. Stock values have to stand on their own merit, and a lot of short sellers lose a lot of money heavily shorting a stock that isn't going to go down. For instance, there was a lot of shorting of BHP-Billiton after the company shut down all Australian iron mining after four deaths. No one appeared to panic, and the stock price remained pretty stable. A lot of short traders lost money in that gamble. Saying that short traders are pushing the markets down is like saying that the Cubs inability to win a World Series is because people keep betting against them.
The stock market is pretty much nothing but the largest legalized gambling system in the world. The thing is, is that the run of short selling on these companies after the news came out helped to accelerate the crash, they didn't cause it, but they didn't help stop it either.
Also, I apologize for the poorly written wall of text earlier, I had been up all night and was kinda pissed because my grandparents lost a large amount of money from their retirement fund. Oh, and if you thought I was having trouble finding a job before...