That's already happened (sort of.) I present to you Cairo, Illinois. It's the most depressing city in America. Here's someone's research project thing about Cairo: http://www.cyburbia.org/forums/showthread.php?t=39039 And here's a backstory thing: http://www.cyburbia.org/forums/showthread.php?t=36105
This kind of pertains to this thread: http://www.futuretimeline.net/index.htm I found this website while researching the chances of a nuclear war (which logically is not certain, but you know us humans), anyways, it kind of looks at trends in society, government and the environment and thinks ahead to what is likely to be, it's good read if you have time...