Cuba is completely free to trade with the other 85% of the world economy that is not the United States, and indeed they've done so since the Soviet Union collapsed. They do quite a bit of trade with various European countries, and in particular Spain.

Interestingly, they're not even 100% cut off from the US- agricultural exports are exempt, and so Cuba imports quite a bit of US foodstuffs like poultry, soybeans and corn. (Farmers generally drive US economic policy!)