How exactly would we lose the electric grid? Nice thing about a distributed infrastructure is that it's, well, distributed.

Also, (nuclear aircraft carriers and submarines|jet aircraft engines) can be (very|relatively) quickly brought into duty producing electricity locally in every city, way before any pandemics and mass starvation.

Longer term, converting from the refrigerated fresh food system of today, to a system based on pickling/curing/canning/iceboxes/etc. is hardly black magic.