I recommend the somewhat dated but utterly harrowing mockumentary Threads, which attempts to speculate on the likely result of nuclear war on an average working-class family in Sheffield, England. It’s somewhat overly pessimistic, IMO, but differs from most other movies in its class by at least trying to consider everything and present a realistic, if close to worst-case, scenario.
I can’t believe I hadn’t heard of it before, and it deserves to be better known.