@anji The car dependency is actually the biggest factor why! It means a significantly higher use (proportional to population) and therefore significantly more wear and tear, thus way more expensive to maintain and resurface constantly, and the result is worse roads.

I think it was Not Just Bikes who had a pretty good set of videos on how a lot of US places are functionally bankrupt due to these sorts of costs. The easiest way to make your roads nicer to drive on is to only use them when they're actually needed...