"All the Major US Cities were destroyed" by the terraforming, then ten years of war.
Sure a lot of duct tape is going to buried and inaccessible, the reserve might not not be evenly spread across the country, but Defiance is a city with maybe 200 people in it.
200 people = city.
Today 200 people doesn't even = a Church mixer.
Is it just me or has 90 percent of the humans in America have to be dead for 200 people to qualify as a city?