It is an interesting scenario, but that isn't civil breakdown. It's is TEOTWAWKI- it is in all honesty beyond the scope of the existing available response.

That being said, as I use it, WWII was a TEOTWAWKI event. Europe has recovered, Asia has recovered. The "Big One" hitting California or Japan, or multiple Class 4-5 hurricanes, or even a limited nuclear exchange would all similarly be TEOTWAWKI events. And honestly, by definition, that while you can prepare supplies and develop tentative plans, it's going to be worse than anyone can imagine.