Foreign investors are scrambling to get their money into the US right now. The rising US net debt is therefore driven more by foreigners' desire to invest in the US than by US demand for capital.

In short, if the PBoC were to actually reduce its holdings of US T-notes, there would be plenty of other global investors lining up to invest in the US right now. China's leaders currently have no blackmail potential.

Sure, that could change. And you could argue that it will change at some point. I have a lot of sympathy for that view. But there is nothing to suggest that such a change is imminent.