Hey, I guess that it's pretty much obligatory to do a Mayan Apocalypse post, right?
For me, growing up as a child of the 70's, the end of the world was ubiquitous. Especially as a gamer and a sci-fi fan.
First, there were the games. As I've spoken of before, SPI had a whole line of "future history games" that essentially played out aspects of World War III, mostly featuring a Warsaw Pact invasion of Europe. I had World War III, Invasion: America, NATO, The Next War, Revolt in the East, China War, Fifth Corps, Fulda Gap, Hof Gap, Red Star/White Star, and many more besides. We played through the Soviet invasion of western Europe countless times, from when I was 10 or so onwards. It certainly made an impression.
My favorite rule came in the Designer's Notes for one game, on the subject of strategic nuclear weapons. I'm paraphrasing, but the upshot of it was, "If you wish to include the effects of strategic nuclear weapons in your game, just soak the map in lighter fluid and apply a match."
Remember, this was the 1970's. Before Reagan and Gorbachev, right in the midst of the ignominious defeat in Viet Nam and the Iran Hostage Crisis. The Cold War wasn't so cold, and a Soviet Invasion seemed like a real possibility, despite détente. America was weak and overt Communist aggression seemed a very real possibility, and we didn't need The Day After or Red Dawn to tell us that would be The End of the World as We Know It.
Then there were the movies. Nuclear war wasn't the only subject, but to see it portrayed by Hollywood, the World as We Know It didn't have much longer. There was biological warfare in The Omega Man and The Andromeda Strain; ecological collapse, famine and corporate corruption in Soylent Green; ecological collapse in Silent Running; out-of-control corporations ruling the world in Rollerball; nuclear war in Damnation Alley; economic collapse and nuclear war in Mad Max; economic collapse and biological warfare in The Ultimate Warrior; authoritarianism, slavery, nuclear war and retro-evolution in the Planet of the Apes movies (all but the first came out in the 70's, so I'm counting 'em as valid for this post); societal collapse and descent into savagery in Zardoz; the threat of nuclear annihilation at the hands of a superintelligent computer in Colossus: The Forbin Project; a generally dystopian authoritarian world in TXH-1138; societal collapse, authoritarian governments with mind-control therapies, and widespread ultraviolence in A Clockwork Orange; and ecological collapse, nuclear war, and age discrimination (although that wasn't a term back then) gone wild in Logan's Run. And of course authoritarian governments promoting blood sports in both Rollerball and Death Race 2000.
Thank goodness Star Wars came along with it story about a genocidal tyrannical government that rules the galaxy, run by a sociopathic cyborg who crushes people's throats with his bare hands, just to lighten the mood. It almost makes one wistful for the gun-totin', human-killin' robots of Westworld.
Still, we made it out of the 70's, and though the specifics of the doom and gloom differ, it's still with us, and probably will be forever. It's the End of the World as We Know it, and I feel fine.