I don't have any control over China's policies. I do have a tiny bit of control over the US's policies, so that's what I concern myself with. I have no choice but to that trust there will be people like me in their respective regions who will do the same in their countries. As you say, it's a global problem, everyone knows that everyone needs to get on board to fix this. Regardless of what other countries do, the US must do its part to solve the problem, or the problem won't be solved. Losing 50k coal jobs is not sufficient reason to prevent the US from doing its part.
You're absolutely right that it's a super big and super hard problem. But we can't just throw our hands up. Even if you're not on board with helping, I beg you to please not stand in the way (or vote for those who stand in the way) of those of us who care about fixing this problem.
Edit: Oh, failed to address this:
> US coal is not going to make a difference whether it continues or not.
It absolutely will! The US is responsible for about 15% of worldwide carbon emissions[1]. Of that, about 25%[2] is from electricity generation. Of that, about 80% comes from coal and natural gas. 15 * .25 * .80 = about 1.8% of global emissions comes from US coal & natural gas power plants alone. Two percent of global emissions is quite a huge amount! It'd be one nice, big step forward on the long, long (long) road to fixing this problem. You gotta do something, or else you're doing nothing, and coal plants are a great target to aim at.
[1] https://www.epa.gov/ghgemissions/global-greenhouse-gas-emiss...
[2] https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emis...