[notacoward]

Two basic explanations come to mind.

(1) Most of Europe had less of a population boom during the time that the auto/highway build-out happened. Part of the reason, ironically, is that there was a lot of migration from Europe to the US. Many descendants of Europeans are stuck in car culture in the US, while their cousins who stayed home are not.

(2) There's a strong correlation between the ability of governments to "spend for the future" on things like transportation and the existence of decent transit infrastructure. It's no accident that Europe's infrastructure is better, Japan's and China's better still, while in hyper-individualist government-hating US it's the worst.

These two factors reinforce each other as well. Most of the "developed" world got out in front on this issue, while we veered off into insanity (thanks lobbyists!) and are now stuck with the near-impossible task of retrofitting The Right Thing onto a well entrenched Wrong Thing.