CNN — On November 20, 1983, a record audience estimated at more than 100 million Americans assembled in a very different TV era to watch a “What if?” movie about nuclear annihilation. That made-for-TV film, “The Day After,” not only served as a highwater mark for the genre but almost surely contributed to hastening the end of the Cold War. Even before the movie aired, the subject matter alarmed the Reagan White House, which feared the depiction of a nuclear strike and its effects on a group of people in Kansas might shake America’s resolve and potentially cause panic. The...