With China now holding $1.55 trillion of US Treasury securities, Geithner must play nice. So far it's working. According to the fed's custody of foreign accounts, the non-US holdings of Treasuries continue to increase (see chart). These are not all the treasuries held by foreigners, but the trend continues to be on the upswing.
Foreign accounts holding Treasuries at the Fed
The US debt/GDP looks horrible relative to last year and the deficit is exploding (see table below). But part of the issue is the lack of alternatives. If you need some place to park your money, your alternatives are Japan, the UK, maybe Germany and France? The rest are just too small for somebody like China. Japan looks far riskier than the US. The UK is getting there as well. Maybe Bundesanleihen? Possibly. But the Chinese may want to hold a substantial amount of Treasuries in order to apply political pressure on the US. - Sure got Mr. Geithner attention.