I suspect one factor here is that the US has, for practical purposes, no passenger intercity rail network, and has a somewhat less developed budget airline market.

That said, I find it notable that the average price of new cars in the US has typically been rising faster than income over the last decade or so. This would indicate, bluntly, effective advertising, rather than resources, being a big driver of the huge car thing. Average new car price in the US is creeping up on average annual income. This isn’t just an American problem, incidentally; it’s happening in a good few countries.