Cuba is a roughly 75 mile x 500 mile island maybe 100 miles offshore from the USA. At Mach 7 that's about 1 1/2 minutes flight time for hypersonic missiles in either direction, maybe 5 minutes for ballistic MIRVS. About 5 x 20-40 megaton warheads would turn it into an uninhabitable moonscape. Just one boomer can easily do this. It's a political bargaining chip for the Chinese, just too bad for the residents.
"We'll fight this war to the last drop of YOUR blood..."