I think the issue in the US is that there are so many guns per capita and the population is so anti authority that it will take generations of confiscation before you'll get a majority of personal firearms out of personal hands.
And in the meantime you've removed the right for individuals to have the opportunity to defend themselves in dangerous situations.
I think the per capita measurement of pollution for China is not really an apples to apples comparison to other first world nations as so much of their population lives in poverty.