What sort of idiot impersonates Chinese police in the United States? To the point of trying to actually pull people over?
Unless (as tomcam says) these are actual Chinese police, blatantly here in the US, trying to tell dissidents "even here we can get to you".
Personally... I'd call the non-Chinese drops and drive as quickly as possible to the closest police station.
No one should ever take someone seriously acting on behalf of a foreign country trying to arrest you in America. Even Interpol needs a USA liaison.
But it makes me feel better about the second amendment.
100% this is a case of dumb kids decorating their cars.
Just saying.