If you're travelling out of BNE, are you planning to travel via the states first, or are you taking the flights via AKL, then into Santiago? If so, you can fly from Santiago to Havannah, or you could travel from Bogota or Mexico City. Alternatively, you could travel through the states to Trinidad & Tobago, then purchase a return ticket from Trinidad to Havannah. But you are right, there is not a direct service from the US to Cuba..(unless you're an alleged terrorist!). American's, as I recall, are actually banned by their government from going there. There are scheduled flights from Toronto and Montreal to Havannah as well.
Bon journey