[I went in and cleaned up this post for clarity--and to add Walter Sweeney's name--in September 2017. China Hand]
Fidel Castro's 90th birthday celebrations might have been a bit more extravagant if Cuba had emerged from the 1962 missile crisis as the world's fifth nuclear power.
Kennedy understood that standing up to the Soviets over Cuba was more a matter of US (and his) credibility and a reflection of US determination over Berlin than an issue of US national security. From the beginning of the crisis, his advisors are unambiguous in their analysis that the missiles in Cuba, when operational, would not effect the strategic balance.
Furthermore, the CIA informed Kennedy that the missiles apparently had not yet been armed with their nuclear warheads (correct) and the missile sites were not strongly defended and could be seized in a military operation with a minimum of fuss and muss (wrong wrong wrong).
The key assumption underlying the US strategy for facing down the Russians in Cuba was that the United States didn’t think that the Soviet Union had any operational nuclear weapons capability in Cuba when it decided to go public and issue the ultimatum to Khrushchev.
As we shall see, Marchetti was right about the strategic warheads that could target the U.S. not being ready for prime time, but the tactical nukes were apparently good to go...
…and here's General Pliyev in his full military fig as veteran of Stalingrad, two time Hero of the Soviet Union, seven time Order of Lenin, Hero of the Mongolian People’s Republic, Member, French Legion of Honor, etc. etc.
The part about the strategic missiles not being operational was something of a lucky guess.
It turns out the the warheads for the strategic missiles were in Cuba but had not been deployed to the launch sites yet.
Another indication that the strategic missiles were not operational in October 1962 is that Khrushchev was not yet prepared to formally announce their existence.
Dr. Strangelove: Of course, the whole point of a Doomsday Machine is lost, if you keep it a secret! Why didn't you tell the world, EH?
---Ambassador de Sadesky: It was to be announced at the Party Congress on Monday. As you know, the Premier loves surprises.
As for the tactical nuclear weapons, McNamara states that his knees wobbled when he was told about them at a thirtieth anniversary get-together in 1992 between the US, Russia, and Cuba. However, it's more accurate to state that he had been informed of the possible presence of tactical nukes on Cuba at the time of the crisis, but had simply refused to believe it.
US planners therefore set aside the worry that a nuke would get lit off in Cuba, and gamed the nuclear element as if it would play out only within the parameters of a potential direct nuclear exchange between the US and Russian homelands.
The assumption was, in other words, that any nukes would have to come out of Russia, and Khrushchev probably wouldn't escalate to global nuclear war if the U.S. dropped the hammer on Cuba.
However, according to McNamara, Kennedy was swayed to go for the quarantine* --> ultimatum --> airstrikes + invasion to follow option instead by the general in charge of U.S. Tactical Air Command, Walter Sweeney, who cautioned that maybe a nuclear-armed missile might survive the massive U.S. strike to hit the United States.
For the Soviet Union, a dismal botch that helped cost Khrushchev his job and, coming on the heels of the China debacle, pretty much put paid to Soviet overseas nuclear junketeering.
What about Cuba? What would have happened if the USSR, instead of putting its own nukes on Cuba, had just given Cuba some nukes? Or, in a strikingly plausible scenario, let Castro keep the tactical nukes after the Soviets withdrew? How would US relations with Cuba and the rest of Latin America evolved?
*There was no basis under international law for the unilateral US blockade of Cuba in 1962. The legal recourse for the US would have been to obtain a 2/3 vote from the Organization of American States authorizing a blockade against a member state, something that the US wasn't willing to wait for. The legal end-around was to call it a "quarantine".