One important detail. And it is very important.
If the US increased its CO2 production, even radically, it would still have strict controls over other gases, that most definitely are poisonous.
China does not do this.
Already for months at a time, the air in Beijing is unbreathable, far worse than American smog in the 1960s, and more like the toxic fogs produced in December in London in 1952, killing 4,000 immediately, with a delayed death rate of 12,000 that lasted until the next summer.
So yeah, China is about to kill a lot more of its people.