"Approval ratings" are rather nebulous. By the divisive and partisan nature of American politics, approval ratings in America are naturally going to be low because both parties exist solely to shit on each other. In China, "approval ratings" get measured from the perspective of "is my life improving?" rather than "would my life be improving more under someone else?"

Honestly? I think asking if someone's life has improved is a more fair polling question to ask, but it's one that's difficult to differentiate in the US because of how radicalized everyone is.

Basically, what I'm saying is that the US would have a higher effective approval rating in the Chinese context than it does today, because many American lives ARE improving under the American government. People just think (often incorrectly) that it would improve more if the other party had power.