That isn’t true. The USA is a bigger producer of carbon per capita, but not pollution, which is defined very differently. This is why hebei cities have many AQI days above a normal 500 yet everyone freaks out whenever AQI in the states breaks 100 during a forest fire.

The EPA has never really bothered that regulate carbon, but they come down hard on the kind of air, water, and soil pollution that exists in China.

Should the USA do more about carbon? Ya, global warming sucks. But the EPA has solved the pollution problem that it was originally envisioned to solve.

The US is a bigger per-capita polluter only because the average Chinese "capita" can't afford to (or otherwise doesn't for some other reason, but knowing Chinese living conditions, I'd bet affordability is the main factor) do/buy/use nearly as many pollution-causing things as the average American "capita".

As a specific example, the US is (according to Wikipedia at least) second only to San Marino in vehicles per capita (910 for every 1000 people). China is in 73rd place, with a much more modest 154. Electricity consumption is similarly different, with the US' per-capita electricity consumption being triple that of China's (despite China having almost double the total electricity consumption of the US).

If the average Chinese had the same purchasing power as the average American, I can guarantee that China's per-capita pollution would skyrocket to beyond US levels.