Realistically, society can make a comeback from pretty much any conceivable catastrophy. Similarly to the situation in communist countries, where important things were scarce and money was worthless, surviving would depend on cooperation and mutual trust, not on defending your bunker and playing out a Mad Max movie. While self-defense has its place I wonder which attitude would prevail.
I agree. Where disaster preparation matters is in that period between "catastrophe" and "recovery". How long before things are normal again? Is that period a week? A month? A year? How bad will it get in between? That's what you need to survive.