You're assuming China is interested in using a strategy that amounts to an economic version of a suicide bombing. On a side note it seems that China has been buying a lot of mortgage securities.. I'm amused - if the really bad version of the housing crash happens the way it will look to me is that the US spent a lot of money buying shiny little consumer goods in China, China will have spent a lot of that money building up infrastructure at home, but also lots of housing in the US in the form of loans that won't get paid back.
A decision by China to crash the US economy means two things: a) the collapse of China's export led model of economic growth b) wiping out all those accumulated surpluses that they've earned due to the export boom.
Sure, it's not the only model available, so they can change. But the sudden forced transition will be at least as unpleasant for them as it will be for the US.
A pleasure I therefore claim to show, not how men think in myths, but how myths operate in men's minds without their being aware of the fact. Levi-Strauss, Claude
Also don't forget the old Chess game saying (from Aron Nimzovitch): "The threat is stronger than the execution" "Ne te courbe que pour aimer..." René Char