Ultimately I think it is one where infrastructure is a bigger problem than individual choices.
In London, yes, you are a shit if you own a big 4x4 to speed around 20mph zones. But also you shouldn't be allowed to, cars, especially ones like that should be banned for personal use (those with a clear need excluded).
In the US, cities need to be rebuilt without the car in mind. Less than 100 years ago most of the Western World was forcibly transformed for the benefit of the car. Huge transformations in infrastructure took place, huge areas of existing buildings were knocked down for the benefit of the car. We did it before, we can do it again, but as a move away from cars. We could over a decade or two massively transform how our cities look and work for the better of everyone, it's not unthinkable, we have already done it once.