That's urban decay for ya. That and many government bodies in the US have a budget deficit and can barely afford (because of some budget fat and people's unwillingness to take even a slight tax increase) to maintain what they've got for roads. Believe it or not, the urban decay used to be much worse in some areas. LA has large swaths of poor urban areas where everything is poorly maintained.
Rural Missouri was like a trip back to the '70s, in my opinion, and I was there in 2007. Florida, not so much, but I was only in the Tampa area, and I was last there in 2004.
An area's wealth affects very much as to whether it looks modern or not. And then there's also the issue of a city/state caring enough about the appearance of an area to maintain it.