It would take extreme desperation for someone like Japan to call in their held paper. That's an entirely plausible scenario though, given their debt loads. How

It would take extreme desperation for someone like Japan to call in their held paper. That's an entirely plausible scenario though, given their debt loads. However, the US could push a button and 'print' $2 trillion tomorrow morning in a monster QE3, and then hand Japan and China each a trillion dollars and nearly pay them off completely. All it would do is probably push the dollar index back down into the mid 70's, where it was 9 to 12 months ago. The bigger problem would actually be confidence, such a move would freak everybody out. Instead the Fed prefers to gradually inflate the value of Chinese and Japanese debt holdings away (which is also why China has taken such a liking to gold).