I cannot see SHTF in the entire US at once. I can see an economic collapse similar to the great Depression. If we suffer a collapse like that, we only have to look to the past to see how others handled it.
Did we have roving bands of raiders?
How bad was crime?
How did city dwellers deal with 25% or more unemployment?
How did electric and water bills get paid?
What was rationed?
I too lived through the threats of the cold war, if that kind of war gets unleashed, you will do what you must to survive, rules/laws get thrown out.
On one hand I really wish I still had my grandpa to ask these very questions. On the other hand I'm glad he's not around to see what's going on. I can tell you this, he was injured and couldn't work for a spell during the GD. That injury kept him out of the service when he volunteered in WWII. He and grandma ate pinto beans and cornbread three times a day for about 2 months. They bartered eggs from a neighbor occasionally somehow. He was making about a dollar a day back then and damned glad to get it, when he got hurt, it put the hurt on them but he was too proud to take any help. My great grandpa was able to provide him some groceries, but he wouldn't take it. He learned from that experience that you never ever spend all you bring in. I went through about 20 years of his bank statements after he passed. They very rarely spent more than he brought in and I never knew him to use credit EVER! When he bought a boat or built his house at the lake, he paid cash after saving for years. Those bank statements should have been used in Home Economics class or something, it was kind of amazing to see. So many questions I'd like to ask him and my Dad.