There's actually a whole body of literature out there on climate justice, if you want to take a look for answers.
One of the primary ones is that most of the developed world has gotten to the quality of life it has today through very high historic emission levels (and continues to have higher per capita emissions). Additional emissions in the West go towards maintaining our very, very high quality of life - emissions in the developing world (like Asia) go towards bringing millions of people out of poverty.
Asia may be the largest polluter by far, it also happens to be the continent with the most people and the most people in poverty.
Nobody thinks that the US is the only country that can save humanity (even if the US cut to 0, that wouldn't be sufficient, although it'd be approaching it), but if the US, which easily emits 4-6x more than most people per capita is unwilling to cut, than we are totally FUBAR on a global scale.