The money that these things cost to the public health service is easily quantified. I expect the taxes to reflect that.
>making low CO2 alternatives much more attractive
If there were "low CO2 alternatives" you wouldn't have to tax stuff, you could just force people to use them, and no one would really complain. Like it happened with CFCs. But taking a train instead of driving your car is not an alternative, it's rubbish.
Bikes aren't an alternative because instead of adding bike infrastructure that costs 10% of car infrastructure, the freaking 6 lane stroad needs a 7th lane, because that's going to solve traffic!
Walking isn't an alternative because US cities and suburbs are largely devoid of trees and any sort of protection from the sun or rain along their sidewalks, if they even have sidewalks to begin with. Oh, trees also make for a nice view and protect pedestrians from bad drivers, instead of lawns everywhere (!!!!). Plus trees and some bushes contain the crazy, deafening, ear damaging levels of noise cars make at speeds higher than about 70kmph.