#China is selling US debt?
Say China sells the US $100 dollars worth of goods. What is actually going on is that China gives the US goods, and China gets dollars in return. If China does nothing, the supply of dollars that China has will increase, causing the relative value of the dollar in comparison to the Chinese yuan to go down. This change in relative value would raise the price of Chinese goods sold to the US, and lower the price of American goods sold to China. 
This is a reality to which China is clearly attuned, since it recently undertook a massive sell-off of the U.S. debt it owned. Between 2016 and 2023, China sold $600 billion worth of U.S. bonds. However, in August 2017 China was the United States' largest creditor, ahead of Japan.