The problem is that your GDP is dominated by consumption and borrowing, not production and savings. Therefore, it's not a measurement of much you have created, but of how much you have destroyed. 70% of the US economy is service based. It has relied on easy credit and house equity to exist. That is changing.

The US barely have any own savings, so the rest of the world have borrowed them their savings. The problem is that the US hasn't borrowed the money to reinvest it. They have borrowed to buy houses, new cars and plasma TVs. When you borrow to invest you will get a capital flow that can be used to pay back the loan. But when you borrow to consume the only way to pay back is with a reduced future consumption. The avarage american will have to get used to severely reduced standard of living as they need to pay back their loans and start building up their own savings pool.