I am sure that was not a fun experience. I asked people to remember what happened after Katrina for a reason. I also ask people to remember that the majority of the population had evacuated.
There will be not be evacuations from our cities so you will have a concentrated population that relies on the government for subsistence.
If any food shortages occur and government services are disrupted there will be riots and looting. Once that happens, most store owners and retail outlets will simply close up shop.
God forbid any of our large cities go “feral” but it certainly could happen based on past history. It will be a good time to live far from metro areas.
People came back in after Katrina, looked around and realized that it was still too uncivilized, and then left for another month or two or three.