It is not that America wants to borrow it, but that we want to buy it ourselves.
At present, the Chinese and American economies are firmly tied together. China is the largest "creditor" in the United States, and the United States is also the largest buyer of "Made in China". At this level, it is also in China's strategic interest to ensure that the US financial system will not collapse.
In the long run, if the monopoly of the US dollar is broken and the RMB is freely convertible, China's foreign currency assets will not be dominated by US debt as it is today. However, under the current international economic structure, China, with nearly $2 trillion in foreign exchange reserves, will still occupy the position of "the number one creditor" in the United States in the short term.