My views of these things aren't in synch with yours in any "political" or security threat way, but I have spent the last forty-plus years of my life researching "sustainable living detached from dependence upon large systems." So, with the olde prof instincts still operating, I'll say that such survival depends mainly upon Energy and sufficient food and water. The energy issue is "solvable" obviously because non-technological peoples have done so for thousands of years. Because we have hi-tech we should be able to turn "survival" into "thrival" if we're clever and modest in our uses. The non-dependent technologies are easy to list: a). PV solar cells if the area is heavily Sun provided; b). windmills if the area is heavily wind provided; c). methane-digester gas if one is husbanding animals; d). geo-thermal heat-of-the-Earth utilization anywhere if willing to put down wells [very small diameter wells] and use heat-pump tech to also get cooling out of it. The geo-thermal reduces the overall demand for space-heating dramatically and if well done can eliminate the need for a furnace almost anywhere --- even in Michigan the dreaded Februaries can be dealt with by Geo-thermal plus super-insulation plus a small electric-resistance space heater in one or two critical rooms. {see Amory Lovins' Rocky Mountain Institute}. The electricity can come from any of the "a b c" technologies. Water heating via passive solar systems is pretty much a no-brainer.
Energy therefore is defeatable by technology and design. Food is more complicated. You have to become a "farmer/gardener" in some serious sense. And unless you want to go severely vegetarian, you must raise some stock [I'd suggest chickens and lambs, although goats are easier than lambs, and you can make cheese.] The livestock is necessary to power any serious garden without trips to access some other high nitrogen source [translation: fertilizer]. Because of this necessity to become a farmer/gardener, few people are truly serious about off-the-grid out-of-the-system living. Frankly farming is hard. Most fantasizers about these matters wave their hands and think that they can store away food tonnages and never do the hard work. Well, the "disaster" better be pretty short [in the area of a few months unless one is a multi-millionaire and building an underground complex or a personal floating city.] The real "solution" to non-dependent living is NOT to go it alone. The real solution to this is to find 60-120 like-minded people who are willing to do some real work and form a sustainable living ecovillage. Then not only can the Energy systems become relatively easy, but the food systems manageable.
If all one wants to do is temporarily dive down into a rabbithole, then I'd rather have a "fly to Costa Rica" plane ticket and save the hassle. If one wants to distance oneself from the big systems, then you're in it long term and "welcome to the soil."