If the damages/externalities caused by cars were internalized by the system car ownership would already be unaffordable for most. We just choose to sacrifice/maim X-number of humans every year so folks can continue to zoom around and structurally increase sprawl/pollution (which in turn have their own massive un-internalized costs).
All of us pay for these subsidies via significantly higher healthcare prices.
Look up what happened to the Michigan laws/policies that required drivers to actually pay for insurance that would compensate accident victims for their death and suffering. It was lobbied/voted out of existence almost immediately because the costs are simply too high, and we love our cars.