The sad and scary thing is that we will need some type of force to handle the gangs of looters that will destroy the cities and then move to the suburbs and then to the country sides when things do go bad.
Chances are the hordes will be stopped within a hundred miles or two of the big cities as they run into well armed country folk, but still, the destruction and death in the cities will be historic.
Chances are that the looting hordes won’t make it further than 10-15 miles from their starting points. There’s going to be a LOT of competition for territory and loot. That’ll whittle the numbers down considerably. The survivors will start to move outward, looking for food. And will fight over it. Which will whittle down the numbers even further.
The remaining survivors will then have to walk ... in small groups ... further out. While hungry and very, very thirsty. And these won’t be folks who are well acclimated to either. They’ll just start going Donner Party on one another rather than continue pressing forward.