For all practical purposes, none. Zip, zero, nada ... Guess what? For practical purposes, they don't produce any drinking water or electric power or natural gas inside the beltway, either. That's sure gonna be fun in August.
2) What happens when free food stops coming into the cities?
What happens when WATER stops coming into the cities? What happens when the power goes down, and doesn't come back up any time soon?
How many gibsmedats will live long enough to try looting the 'burbs and the country?
Arguably.