Greetings Mr. Ritter. Here's my long-winded, rambling answer to your short question.
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In many urban areas, barring zombies or total nukes, I suppose supply chains might start to rebuild within three weeks. There is big money involved, and they are highly motivated. You might not get what you want, but you are likely to get enough to avoid hunger. It helps if you have the option to be mobile -- not everyone has that option.
There is a growing movement to move city lots back to what they were a century ago -- with a big kitchen garden up front and laying hens in the back yard. Local busybodies and bureaucrats push back, but I think they are slowly losing as people fight tooth and nail against the rising cost of everything. Cities don't have to be deserts.
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We're in different circumstances: we live in the country (by choice) and we grow a portion of our food anyway, and harvest wild goodies, and store it all. We could easily ramp that up in case of interesting times. So our "preps" are pretty much part of normal operations, in line with what my parents and grandparents did, and their parents and grandparents before them.
We have water sources on site or within a few minutes' walk, and given our infinite firewood we can boil up as much as we need. I cook my own charoal (biochar) which can help with filtering if needed. If we ever need to bug out for a week, we have family with similar resources within an hours' drive. And bins of wheat, if it comes to that.
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I've chatted with people who have a bunch of freeze-dried stuff in their basement. Set it and forget it they say! Well maybe it's a good idea -- hungry people do desperate things. But I am not convinced it is wise. Those packages that claim "a year for four people" look like about 2-3 months' food to me. After that, they say their plan is to hunt and plant a garden. If they haven't put in the time and effort to learn those skills, the results will not be happy. Game that is relentlessly pursued will be as hard to find as the Loch Ness Monster. Gardens (a.k.a. micro farms) don't magically kick out protein and the necessary millions of calories even if you do have a few packets of seeds.
I notice that in the fall, storable staples like potatoes, carrots, and beets are cheap like dirt. Onions too, if you dry them down for a couple of extra weeks. Every house could have a cold room, if they had the will, with a 6-month store of essential calories for pocket change. Saves money, adds resilience.
I personally think anybody who makes an effort to learn pioneer skills and to use the dirt-cheap dried goods (peas, lentils) at the supermarket couldn't starve if they tried.