I'm struggling to find the original document/page I read on this, but largely, "a car having better parts is due to the road having features that benefit these parts due to generations of studying the way cars behave in that set of circumstances.

Autos are designed around and for the roads they will serve, not vice versa. This is the bane of auto manufacturers who want to make one tail light housing for all their cars in all their markets.

it's a bit more easy to read data comparing for example safety in Euro market vs American market (there are fundamental differences in safety thoery; lighting, ride heighgt, weight, engine size etc. As opposed to looking at changing trends in one market over 20 years, which are largely stylistic.)