Per capita emissions is not the right metric. It seems like it should be, but if you compare by that metric you're really measuring poverty below a certain threshold. A poor nation might have low CO2 per capita just because it's poor, but what production they do have could be fantastically inefficient (and often is due to old technology). As they climb out of poverty, as all seem to be doing, they'll become huge emitters.

Emissions per GDP is probably the best we have as GDP is a decent proxy for productivity, making it a real measure of efficiency. If the goal is to actually reduce emissions the goal must be to reduce CO2 emitted per unit of productivity, so you want to emulate the wealthier nations that have low CO2/GDP scores. That means emulating policies like renewable energy, efficiency standards, well designed cities, etc.

China is (last I looked) the least efficient large economy in terms of pollution per GDP. The USA is toward the middle of the pack.