Confusion between a government holding debt, and a holder of government debt notwithstanding, a state actor can also hijack an airplane and ask for a billion dollars, or they will kill a hostage every 30 minutes.

Or, they can threaten to nuke South Korea if you don't send them food.

As it's not ran by people with the financial and diplomatic acumen of either the Tea Party, or the Kim family, China's not likely to do either.