As if the real Cold War threat of nuclear destruction wasn’t enough to scare the wits out of children and teens, there were also the nuclear war horror movies of the time. Perhaps the first, and one of the most famous, was Godzilla, an enormous, violent, prehistoric sea monster awakened and empowered by nuclear radiation that wreaked destruction on entire cities and breathed radioactive fire.
Another 1950's "nuclear monster" movie, and the first "big bug" film, was Them! About giant irradiated killer ants threatening to take over the world.
A slight twist on the theme was “The Day The Earth Stood Still,” in which a peaceful alien arrives on Earth to warn that if the human race doesn’t cease its (nuclear) warlike ways, a vast galactic group of peacekeepers will have to destroy it.
Other movies dealt with fear of radiation or attacks by zombie-like humans who served as metaphors for the brain-washed communists we would become if the Soviet Union won the Cold War. They included The Beast From 20,000 Fathoms (1953), It Came From Outer Space (1953), The War of the Worlds (1953), Creature From the Black Lagoon (1954), Tarantula (1955), Forbidden Planet (1956), Invasion of the Body Snatchers (1956), and The Incredible Shrinking Man (1957).
Clearly, visiting aliens had a thing for women in nightgowns with lace trim.