Why is distance of Cuba to Florida significant?

In the cold war, the short distance between Cuba and Florida meant that Cuba, a communist country that was friends with the Soviet Union, could launch missiles at the U.S. without having to design super-long-range ballistic missiles. The question became, "How many U.S. cities are within missile range of Cuba?"

Nowadays, the major concern could be with Immigration and trade. Not only do many Cubans try to sail illegally to America, but the trade embargo the U.S. has on Cuba means that there is a lot of smuggling going on.