"people claiming to be law enforcement from China"
Let's imagine for a second that they actually are.
That still doesn't give them the right to enforce Chinese law outside of China. Not without a treaty between the USA and China and, these days, I really don't think that kind of treaty has any chance of becoming reality.
Someone can very well show up at my doorstep in France and claim to be from the FBI. He can even show me his card. He is not the law in France and any menace will be met with a curt "Out !" and that will be the end of the story for me.
It will be followed by a call to actual French police to warn them that there is a guy impersonating US FBI agents and going around threatening people, so that might not be the end of the story for him, but that's no longer my problem.
Of course, I have no more family in the USA to be threatened with, so there's that.
Even if China is actually sending proper law enforcement officers to try and get Chinese criminals to go back, that's not the way you do things. You negociate and extradition treaty and, once signed, you then submit extradition requests via the proper channels. But of course, that would mean China plays by international law, which is something it has a very hard time doing as soon as said law is not in its percieved immediate interest. That is how we get a nation acting like a schoolyard bully. And that including toward its own people.