You could get a few stray drones exploding over the US mainland but do you think it would stop them from invading?

Cuba can’t produce any significant amount of drones without imports. Being an island in the US backyard they can be blockaded with ease. Iran can still import their stuff over land.

It’s relatively easy to bomb every launch site on a tiny island compared to Iran.

It’s also easier to cover every path a drone could take from Cuba and still reach anything of value. You have tons on well supplied air bases that can use relatively cheap munitions launched from fighters instead of using dwindling supplies of patriot missiles.