I suspect that people tend to buy an automobile that they can afford and that's comfortably-sized for the infrastructure such as typical lane widths and parking

I suspect that people tend to buy an automobile that they can afford and that's comfortably-sized for the infrastructure such as typical lane widths and parking spaces. In much of the US, that comfortable size is the Ford F-150 (a Hummer H-1 is too wide, a Toyota Yaris is unnecessarily small). In most of Europe and in some urban areas of the US, the infrastructure is smaller, so automobiles are by necessity smaller.