^^^
Because america isn't responsible for 1 city going downhill because of it's residents' actions.
For its residents actions? Are you kidding me? Detroit is in the shape it is now because of post-industrial age america, corruption, and its dependency on car manufacturing. Detroit used to be a booming city, say during and before ww2. It manufactured most of the army's vehicles and before that it had been growing slowly.
But once ww2 was over, we cut back a stuff ton on our military, and Detroit stalled. I mean, look at Camden. It seems to be the same example, actually. Camden used to be the busiest port
in the world during ww2 and the industrial age. After that, everyone retreated to the suburbs and Camden stopped producing anything due to their dependence on making ships.
You cannot blame this on the people. Detroit is one of the largest cities in the US. Detroit might be crumbling, but eventually we'll find a way to fix it, even if it puts us in more debt and if it takes a lot of effort.
EDIT: Also, much of Detroit has little to no population. They really need to cut back on the land. On another note, we're all still trying to figure out what to do with Detroit. It will take time, but it is inevitable that something will happen. We can't leave 700,000 people in the dust.