I listened to an interview once of a person that survived when their country was cut off from supplies during a war. Somewhere in the middle east but I forget which country it was. One thing he pointed out was the necessity to band together with either family or some very trusted neighbor to work together. He said when things got really tough one or two people could simply not keep up with surveillance of the property 24/7. People eventually have to sleep. Can't remember for sure but I think he said needed 4 or 5 people minimum to maintain a long term (months) stronghold. He said the houses than only had a couple people were picked off one by one over time. His situation was people of his own community, people that otherwise in a better situation would never do the things they did. But the country was completely cut off from supplies and it basically became survival of the fittest. Another thing he said was some of the most fortified looking places got picked of pretty early. People would gang together to break in because the place looked like it had good things to hide (mostly food and medicine). He pointed out keeping a low profile was important. Don't stick out. The currency became cigarettes, canned food, toilet paper, things that could be traded again for necessities.

I don't think such a problem will happen here in my lifetime, but if the politicians don't quit promoting racial hate and division, I suppose anything is possible.