I'm quite sure the US can handle an extra 10 people (illegal aliens are people too aren't they?)
What happens if China sells all of its U.S. Treasury holdings?
A big nothing.
China has already divested itself of half a trillion dollars in Treasuries.
Furthermore, during this period, the Federal Reserve has trimmed its balance sheet by $1.3 trillion, yet the system continues to operate smoothly.
Given this trend, China could potentially minimize its holdings without significant impact.