You speculate what the US would do if Cuban planes were violating our airspace and dropping leaflets, but you ignore actual history of our airspace being invaded for years without planes being shot down. You see, drug smugglers have been flying planes into US airspace dropping stuff a lot more dangerous than a bunch of frigging leaflets AND WE DON'T SHOOT THEM DOWN! The military works with the Customs Bureau to attempt to intercept and track these planes. I've seen many examples of IR or night-vision video where the planes are followed into the US. These planes then either land at some out of the way airfield or drop their bundles to waiting vehicles on the ground. I dare you to find a single example where the US has shot down one of these planes.