The sputtering U.S. recovery is worrisome enough. Now a looming slowdown in China, the world's growth engine, threatens to make things worse. Faced with rising inflation fueled by what appeared to be a real estate bubble, Chinese authorities have been hiking interest rates and clamping down on credit, which has put the brakes on gangbuster growth. Some predict China's economy will slow to a relative trot of 8.7% growth next year, down from 10.1% in 2010. That spells trouble for countries that supply China's export machine, like Thailand, Vietnam and Germany. The impact on the U.S. won't be as big. American exports to China are growing but account for only 4.5% of the total. Falling demand from China could lower commodity prices, hurting U.S. industries like farming and mining. But it could also help U.S. consumers, especially at the pump.