The population density of Sweden is lower than the US and it has excellent roads.
I'm not saying that states with bad roads don't have themselves to blame, just that density is a factor.
You're saying that it's got more to do with how much the population is willing to be taxed, which I believe is the real reason.
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.
One summer when I was living in Philadelphia they removed the surface of the road in front of my apartment. Two months later they put it back. And if it's not that, it's crews filling in holes from road-work with about half as much asphalt as the hole needed, or the random patches of cobblestone street still left in the city, seemingly with little rhyme or reason.
Now, I think that's a pretty fair comparison. The roads can be pretty terrible in Washington and Oregon from my experience. That may be because federal money for roads goes to other less dense states, but these proportions hold up fairly well nationwide too. I think it's just a matter of less public funding, it's that simple.