When I was a child, my school would have nuclear attack drills, which involved quickly climbing under a desk of walking quickly to the basement of the school. I think the general strategy was to go somewhere special to essentially kiss your ass goodbye.  That was in the 1960’s where a neighbor in Florissant had actually built a bomb shelter in the front yard, and you can still see the entry to that shelter.  In the decade since the 1960s, I’ve gradually stopped thinking so much about the world’s arsenal of nuclear weapons, even though they are extremely dangerous to possess, even for a country that has them for the supposed purpose of using them against another county.

See time code 1:17 of this excellent documentary by Eric Schlosser, “Command and Control,” where it is revealed that a declassified military report indicates that there have been more than 1,000 U.S. accidents involving nuclear weapons, at least 31 of these posing serious risks of accidental detonation, risking the lives of countless Americans.

It is a miracle that none of these have resulted in nuclear detonations. From the American Experience Website: “Based on the critically-acclaimed book by Eric Schlosser, this chilling documentary exposes the terrifying truth about the management of America’s nuclear arsenal and shows what can happen when the weapons built to protect us threaten to destroy us.”

All of this was brought to mind while I was listening to a Sam Harris podcast interview of Lawrence Krauss (I’m referring to the final 30 minutes of the podcast). Krauss mentioned that the “Doomsday Clock” is now 2.5 minutes to midnight. From the Doomsday Clock site:

Last year, the clock remained at 3 minutes. Today, it moves half a minute closer — the closest to midnight it’s been since 1953.

The Bulletin cited two troubling concerns in their decision: the growing disregard for scientific expertise and the “cavalier and reckless language” used around the globe, particularly during the U.S. presidential election.

Which brings us to the elephant in the room: Donald Trump, a man who appeared to have called for a new nuclear arms race and has failed to show an ounce of restraint from the election to the White House, now has the absolute authority to launch a nuclear attack. Thousands of nuclear weapons can be fired within 15 minutes of Trump ordering a strike. He doesn’t need permission from Congress, his Cabinet, or anyone else to start a nuclear war.

Near nuclear disasters don’t only happen in the American military. A Soviet sub commander named Vasili Arkhipov likely saved civilization, taking an extremely brave stand in the face of immense pressure in 1961. This account is from Wikipedia:

Vasili Alexandrovich Arkhipov (Russian: Василий Александрович Архипов) (30 January 1926 – 19 August 1998) was a Soviet Navy officer credited with casting the single vote that prevented a Soviet nuclear strike (and presumably all out nuclear war) during the Cuban Missile Crisis. Such an attack likely would have caused a major global thermonuclear response which could destroy much of the world.[1] As flotilla commander and second-in-command of the nuclear-missile submarine B-59, only Arkhipov refused to authorize the captain’s use of nuclear torpedoes against the United States Navy, a decision requiring the agreement of all three senior officers aboard. In 2002 Thomas Blanton, who was then director of the US National Security Archive, said that “Vasili Arkhipov saved the world”.

. . .

When discussing the Cuban Missile Crisis in 2002, Robert McNamara, who had been U.S. Secretary of Defense at the time, stated “We came very close” to nuclear war, “closer than we knew at the time.”^[14] Arthur M. Schlesinger Jr., an advisor for the John F. Kennedyadministration and renowned historian, continued this thought by stating “‘This was not only the most dangerous moment of the Cold War. It was the most dangerous moment in human history. 

See also this account of this near-tragedy.

The United States and Russia each have several thousand nuclear weapons.  See this list at Wikipedia for more about the nuclear stockpiles of the various nuclear-armed countries.

To map the destruction of various kinds of nuclear weapons on various cities this website offers many options.