The terraforming was complete.
They said that every city was demolished, but considering the importance and rise of New York, I'm thinking that every city on the mainland was destroyed. The water would have protected the islands that make up New York City, and other cities off the coast land.
But the mainland would have been frakked.
The interstate highways are gone.
The railways are gone too.
And Air travel is impossible, or too dangerous.
They can build factories and whatever, they're not stupid, but the only reliable method of mass freight transit they have is boats. So it's almost impossible to disseminate any freight of any classification to any "city" more than a few miles from a large water way.
They wouldn't build a city where Defiance is except for the mine.
Even with the mine it's still a stupid place for people to live.