You have oversimplified the situation on a grand scale. Trillions of dollars disappeared thanks to the collapse. Those trillions have to be put back. The American consumer faced with their biggest asset, their homes, plunging in value and with wage growth trapped at 1-2% and credit card debt at records highs, savings at record lows they simply have no leeway to spend more. Export driven countries like Germany and China will one day have to actually start buying themselves or else it's all going to go bust.