Right but USD is untouchable. The only way it could simultaneously cause a catastrophic event in the US and China is if its value collapsed, and that won't happen because it remains (and is poised to remain) the world reserve currency for at least the next few decades. The only other contenders (renminbi and Euro) are in no position to assume the mantle (unstable economy with no track record of prudent fiscal management and recent track record of amateurish fiscal management and.....well, the Euro
).