As this isn't a list of things the U.S. finds prudish, but actual images of children involved in being/becoming a victim of abuse, it doesn't look like there are borders, at least according to the official Apple explanation[0].

If the situation OP suggests happens in the form of FBI/other orgs submitting arguably non-CSAM content, then Apple wouldn't be complicit or any wiser to such an occurrence unless it was after-the-fact. If it happens in a way where Apple decides to do this on their own dime without affecting other ESPs, I imagine they wouldn't upset CCP by applying US guidance to Chinese citizens' phones.

0: https://www.apple.com/child-safety/

It’s still a US database, and from it’s goal it would fit US defintion of child abuse.

I am no expert of what it means to the US, but I’d assume there can be a lot of definition of what “child”, “abuse” and “material” mean depending on beliefs.