Off-grid cabin. Learn to build, farm, hunt food, and machine tools.
https://www.ted.com/talks/irwin_redlener_how_to_survive_a_nu...
Not only that, the IRS has plans to resume operations no more than 12 hours after such a war:
>The IRS must have the capability to be fully operational at its continuity facilities as soon as possible after the occurrence of an emergency, but not later than 12 hours after continuity operations activation.
Shelters was systematically not invested in in my country, and sirens somewhere works somewhere not.
It all depends on what level of tech you want to live your life. But civilization as we know it would be over for the foreseeable future. Famine would be almost certain.
I was reading about it recently and came to that conclusion, so asking the question sincerely, looking for a more informed opinion/understanding.