In a nutshell this is what ended the Cuban missile crisis.
This does not include the huge stockpile of nukes in our bomber force, the weapons we had available on our CVs, the Polaris SSBNs "the soviets had no such subs at the time". Had the Soviets used one of those Cuban nukes they would have had to face an American retaliatory strike of about 3,500 weapons. They would have been out numbered in both nukes and yield by about 17 to their 1. In short they would have suffered less casualties shooting their own nukes at themselves then they would have at us. The strategic balance of forces is what ended the crisis.
And it was what started it. They thought they could equalize the game by putting IRBM and gravity weapons in Cuba. They had sent 40,000 troops as well to help protect the Island and the crisis ended up going hot. They shot at our reco aircraft and even downed a U-2.
The world was on the brink thats for sure.