USA is doing terribly thanks to having by far the largest emissions per head, dramatically in excess of anywhere else.
Asia is doing poorly thanks to having larger populations, developing apace and being home to much of the world's manufacturing.
UK is just about world's worst for historic cumulative emissions thanks to being home of the industrial revolution.
Shall I go on? It's everyone's problem, and needs addressing everywhere, at every election. Anything else is just finger-pointing excuses not to act.
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.
It's easier to reduce 1 ton of annual CO_2 emissions when you're producing 17 tons per year and person (like in the US) than when you're at 6 tons like the Brits. In either case, it would be 1 ton saved per year but it's only a 6% reduction for someone in the US but a 17% reduction of their yearly emission for a Brit.
- China is taking concrete steps to reduce emissions: capping coal production, switching to electric buses, et cetera
- For better or worse other countries are far more likely to say "why should we reduce emissions if even the US won't" than to say "why should we reduce emissions if China won't".
Don't forget that a lot of that pollution is due to production for western consumption.
That doesn't mean that US policy can't address the problem; US policy—on climate as well as most other things—need not be limited to domestic policy.
Russia and China are not fighting against the sort of collective action we need to take?
Meanwhile, the Anglo-West is hyper-focused on the US because there's a president they don't like. This has been a blessing (now the average Anglo-Westerner at least pretends to care about the environment), but also a curse (they think the US is the only country that can save humanity).