More information
A detailed chart of foreign holders of Treasury securites here.
Main page here.
China has, as I suspected, moved up in the ranks since 2007, but they still only own about 7 percent of the debt (the total debt in 2008 was about $10 trillion). If we add in the oil exporters (again, assuming all are hostile), and Russia for good measure, the total percentage held by hostile lenders would be about 10 percent.