I largely agree about the insanity of our highway subsidy, but I can see some of the logic in it. Cars are more convenient/practical in rural areas, and the US is pretty rural (I think it's stupid and short-sighted to encourage rural development via highway subsidy, but that's another rant).
That said, in most of the developed world, the competition is between planes and trains. Cars are more expensive (probably because they're not as heavily subsidized).
> Cars are more convenient/practical in rural areas
Not really true. It only seems that way because of the development pattern subsidized highways have enabled. In much of the world housing is clustered in dense towns in rural areas. This was the normal development pattern in the US in the 1800s. Rural towns were fairly dense and walkable. The productive land was around the town. The housing was not needlessly spread out through the productive land.
Well, yeah. I think we agree, and that's what I meant when I said that rural development subsidy is stupid.
Still, the US is a lot bigger than, say, France or Germany. It's harder to build comprehensive train systems between urban areas here (particularly in places like the west).
That said, in most of the developed world, the competition is between planes and trains. Cars are more expensive (probably because they're not as heavily subsidized).