I think the missiles were about to go operational and the blockade prevented it.
If they had been operational, the nuclear side of the equation would have been more complicated but the Soviets already had substantial capability over the pole. I think Kennedy was actually blocking that increment in their capability. The timeline of the SIOP is very important. I think he didn't want his decision/action time crowded by the difference over the pole or from a sub as opposed to Cuba. It was more complicated back then because the subs didn't really have a high p-kill against a hardened target compared to land launched. Presumably the Cuban missiles would - like we had in Turkey.
I knew of course about the U2 being shot down but not about the Soviet sub. The detail of that will be very interesting. Must have been an interesting moment on that sub.
When I was in the US military I had a US artillery officer from the European theater say...close paraphrase...."Any officer in Europe who would wait for authorization to nuke a Russian advance would not be worth his salt". It shocked me because I always thought that the decision to go nuclear was reserved for the president.
Also found out that it is very important operationally in the event of an invasion from Russia into Europe to go nuclear immediately. Else you end up needing to nuke your own troops. This was discovered in early computer battle simulations. If they move, we nuke them right away.
Of course the idea that the Russians would not first strike is crazy. That whole scenario of them trying to test their conventional superiority by an armored assault through the gap is just stupid. Used to crack me up watching junior officers puzzle over how they would fight it. We are so wide open to first strike by a small force distributing nukes, that they would almost surely carry it out. Back in the day I actually sailed a boat into San Francisco bay and touch an aircraft carrier unmolested. Bet I couldn't do that these days!
Technically, deterrence functions by denying your opponent the option to escalate in the hopes of an improved outcome. But I have always thought that the word "improved" was a little ambiguous. If I executed a counter value strike, simultaneous time on target against every US city with population greater than a million with very high probability of kill, I would have denied the people in the silos and the subs hopes of improving their outcomes except by negotiating with me...in a sense.
But how many would stand by. I think they would launch just to get even. In other words "an improved outcome" might be both countries destroyed not just my own and me getting some sweetheart deal in Moscow. Many of the US officers were, presumably are, motivated by nationalism. They are not just glory seekers. They have love of country infecting their emotions and are quite capable of killing out of wounded sentiment.
Anyway, the current nation state system is ridiculously obsolete. We need to free up the resources, get people fed, clean water, education for a generation or so, festivals everywhere (circus) and security, security, security. A big part of that is how to restrain those at the apex of any hierarchy. Clubs, religions, government, business, whatever. Zero freedom to organize anything clandestinely - with very stiff penalty. Take privacy away from those dominant in any hierarchy and protect the privacy of the unorganized. Really look at ways of restraining police forces without disabling them. Remember that Hitler started his rearmament with neighborhood clubs organizing.
Socialism might not work but unbridled capitalism surely won't either. Need to make it one man one vote, not one dollar one vote. Or some meritocracy where you have to pass a basic test to vote or something. Where are the political scientists who are supposed to think this stuff up!?
For example, imagine that after we go global we have all police officers operating only with a second "shadow" officer whose job is basically to be a press officer, document what that officer does that day and put it out for all to see. If there is an investigation needed the press is embedded in it and records and publishes after the event when they decide. The press officer has arrest authority on the police officer he shadows. The police officer has a weapon and can use it unless the press officer decides to disable it with some button he has. If the press officer is not near the police officer the police officer's weapon disables automatically.
As for those at the apex's of any organization, they loose their privacy as they go up. Someone like the president can be with his wife in a communication proof room, or can take a dump in one, but cannot speak or communicate with anyone except on the internet. We do that and really break the government up into pieces and we may be able to manage.
Then we just need to worry about the mob!
We really need a kind of Rousseau, to think through the new rights we need to put in place. For example, no generation should be able to rape the planet and destroy its resources then die to avoid the consequences.
It is very challenging. What is for sure is that what we have is not stable and will, is, leading to disaster. Where are the political scientists identifying the ideal political systems given homo sapiens sapiens instincts and talent distribution?