So - which hypothetical scenario is involved here ?
i. If Cuba were to launch *non* nuclear Russian supplied cruise missiles at the US mainland ?
ii. If Cuba were to launch Russian made missiles armed *with* nuclear warheads at the US mainland?
Two very different scenarios - neither of them remotely plausible, or worth any serious discussion.
It is worth noting, even at the height of the 1962 Cuban missile crisis, that the USA never once considered launching any form of missile strikes on Cuba, even though American U2 surveillance flights had detected 9 launch sites for Soviet missiles with thermonuclear warheads being prepared on Cuban soil. The American military options were confined to conventional airforce and naval bombardement, followed by an amphibious invasion: or a naval quarantine blockade of Cuba.
It later emerged that in addition to the IRBM missiles, the Soviets also had up to a dozen 9K52 Luna-M (Russian Луна, - ‘Moon’ ) short range artillery rockets armed with 2 Kiloton tactical nuclear warheads. The presence of these weapons code named Frog 7 by NATO was wholly unknown to American intelligence, or to US secretary of defense Robert Mcnamara.
https://en.wikipedia.org/wiki/9K52_Luna-M
These tactical nukes were under the control of Soviet forces on Cuba whose commanders were tasked with defending the Cuban missile sites, and they had command authority to launch them on their own initiative, without consulting the Kremlin in an emergency. If America had proceeded with the large scale amphibious invasion of Cuba recommended by JFK’s generals, then their invasion force could have been devastated with multiple tactical nukes, and WW3 would have ensued.