I guess what I'm saying is that while dodging the real cause of this issue, Americans are going to point to large geography rather than large population as the 'root cause'. In this case that isn't entirely without merit, since for a lot of Americans (those in Maryland for example) the '(tax rate * population) / area' equation works out alright.
I'm not saying that states with bad roads don't have themselves to blame, just that density is a factor.