Cuba had more nuclear warheads on the island in 1962 than the US knew about.
If JFK had listened to his military generals and launched an attack, it would've spelled disaster.
A large portion of the US Eastern Seaboard (New York, Washington, Miami, etc.) could've been hit by nuclear weapons, Cuba would've been destroyed in retaliation, and the USSR would've almost certainly invaded Europe immediately beginning with West Germany, possibly using further nuclear weapons to demolish Europe as a response.
This is why temperment of a president is important. This stuff isn't a joke, and it's not on advisor's to make the final decision. A president has to have the courage to make the call on his/her own even when 12 other people in the room are telling him/her otherwise. Hopefully we never, ever find ourselves in a situation that precarious ever again.
The irony is in this (dark) time line, JFK probably does not get assasinated in Nov. 1963 as obviously things would've been radically different, he certainly wouldn't be campaigning in Texas in the midst of World War III. So he saved the world, but probably set forth a time line that resulted in his assassination one year later.
