The US is now facing double whammy, with no major treasury purchases happening from China and Japan in the last few months. So far, these two countries were investing billions of dollars of their trade surplus every month, into buying US treasuries.
But with their exports to US crashing, their trade surpluses have vanished, and they are also seeing a declining yield on their trillions of dollars of investments.
Now US is seeing clear signs of delay in local economic recovery. Hence, the US is now asking China to do everything to boost their local demand. US badly needs a economic recovery, for which it wants a healthy Chinese economy.
If China is unable to get a local demand boosting, which is good enough to cover the gap created due to crash in US exports, then it can trouble the US also indirectly.