The first takeaway is that Chinese pollution is really, really bad. Even the smoggy California cities the US worries about have less than 20% the PM2.5 readings of the Chinese cities at the bottom of their list.
The second takeaway is more interesting. If China’s “light” pollution level ends at a point where the US index is already deep into “unhealthy”, it means that the Chinese government is, even when trying to solve the problem, going to drastically understate just how bad this is. My guess is that even if the Chinese government gets to a point where they declare victory, their worst cities will still have PM2.5 ratings triple or quadruple that of a city like Los Angeles.