>They don’t provide an enclave where civilization can regroup and rebuild collectively.
Your model of nuclear war is flawed, which is understandable given the immense amount of misinformation out there.
If Russia and China launched every nuke they have at the US, about half of Americans would survive even without any use of fallout shelters. Most vehicles would "survive" (continue to operate or fail in ways that are easy to fix even under the new, degraded conditions in the country). At any given time, the US has enough food stored (mostly in the form of grains and soybeans intended to be fed to livestock) to keep the survivors alive for 3 years.
In contrast, you seem to think that most people in attacked countries would die. Either that or you think most of the survivors would degenerate into a distinctly uncivilized mode of living, which is also unlikely IMHO. I can elaborate on this point if there is interest. My prediction is that the period of social chaos lasts only as long as it take for the radiation from the fallout to diminish to non-lethal levels, which is about 3 weeks after the last weapons exploded. (Less than half of the area of the US would be covered by lethal concentrations of fallout in the first place: fallout shelters are a good idea because there is no location guaranteed not to receive lethal levels of fallout: it literally depends on which way the winds are blowing.)
The big unknown in an all-out nuclear war is nuclear winter, which might end up causing most of the deaths, i.e., after the silos full of livestock feed are used up, but IMHO it is unlikely that nuclear winter would be that severe.
In summary: nuclear war will not cause a collapse of civilization or societal order, at least not one sustained for more than a few weeks or possibly a few months.
Your model of nuclear war is flawed, which is understandable given the immense amount of misinformation out there.
If Russia and China launched every nuke they have at the US, about half of Americans would survive even without any use of fallout shelters. Most vehicles would "survive" (continue to operate or fail in ways that are easy to fix even under the new, degraded conditions in the country). At any given time, the US has enough food stored (mostly in the form of grains and soybeans intended to be fed to livestock) to keep the survivors alive for 3 years.
In contrast, you seem to think that most people in attacked countries would die. Either that or you think most of the survivors would degenerate into a distinctly uncivilized mode of living, which is also unlikely IMHO. I can elaborate on this point if there is interest. My prediction is that the period of social chaos lasts only as long as it take for the radiation from the fallout to diminish to non-lethal levels, which is about 3 weeks after the last weapons exploded. (Less than half of the area of the US would be covered by lethal concentrations of fallout in the first place: fallout shelters are a good idea because there is no location guaranteed not to receive lethal levels of fallout: it literally depends on which way the winds are blowing.)
The big unknown in an all-out nuclear war is nuclear winter, which might end up causing most of the deaths, i.e., after the silos full of livestock feed are used up, but IMHO it is unlikely that nuclear winter would be that severe.
In summary: nuclear war will not cause a collapse of civilization or societal order, at least not one sustained for more than a few weeks or possibly a few months.