It's interesting to see that there are several countries that emit more per capita than the USA, including Canada and Australia. Maybe the USA should stop trading with those countries?
The optimal place to focus effort is wherever a marginal unit of effort has the most impact. I’m not aware of any research that estimates that, and while I won’t be surprised if some cities in China are more important targets of effort than some cities in the USA, I’d also expect a unit of intervention in a randomly selected city in the USA to be more effective than “the same”[0] intervention in a randomly selected city in China.
[0] adjusted for exchange rates, etc.
How is that metric useful in any way, besides deceiving people and accuse other countries of being the bad guys?
It's industry which pollutes, not people. That's why it's so pointless to blame plastic straws and other silly things like that.
Maybe if we stopped buying things from communist China things would go better.