Target lists of other nations do not include all large metro areas in the US. A list for Russia was leaked once; by NY, LA, Seattle, but the middle of the country was mostly untouched. Presumably local infra in many areas will be disconnected from the old larger grid but locally intact.

Still functioning gadgets with WiFi will be all over and can make a local mesh network. Dams, wind turbines, utility lines, will remain.

It’s not aliens with doomsday weapons hitting all human occupied places from space.

That said it’s really what survivors do about that. Not hard to see many in shock ending themselves given the lack of hands on survival skills, and connection to the manual labor that keeps us alive, like farming.