Like I said, we could argue that the fed changing rates is different, and I wouldn't completely disagree with you. But if you put your self in the shoes of China, the Fed is pursuing a "self-serving purpose" of optimizing the U.S. economy, just like they are pursuing the purpose of optimizing theirs. It becomes splitting hairs, to anyone but you and I at least, to argue it's independence from Congress and President makes it not representing the U.S. government. While perhaps technically true, it unquestionably serves U.S. interests.
The latest FOMC minutes actually mention trade and currency valuations a number of times, just to grab the first set I could find:
https://www.federalreserve.gov/monetarypolicy/fomcminutes20190619.htm