> The US is plenty wealthy per capita

This is not a particularly useful statistic when talking about the number of cars being bought.

Almost invariably, "per capita wealth" uses mean wealth. This is dramatically different from the median wealth.

When you've got a few individual people worth upwards of $200 billion, that means that each one of them adds roughly $1000 to the "per capita wealth" number, while only ever accounting for something like a dozen cars at the outside.