they are when that one country represents nearly their entire customer base.
Sure, the US is important to China, but "nearly their entire customer base"? Ahh... EU is larger than the US to China (see http://www.stanlib.com/EconomicFocus/Documents/Global/ChinaexportstoEUvsUS.pdf). But agreed - letting US go bankrupt would definately be a hit to the Chinese economy.
The world is moving so fast these days that the man who says it can't be done is generally interrupted by someone doing it. -- E. Hubbard