SomeGuy said:True, the US considers it "Trading with the Enemy", and if you try through Mexico or Canada they will turn over passenger lists so thats no good either. You can go through some of the south american countries as their relationship with the US is strained and they won't cooperate. You can arrange for someone to meet you at the airport with a ticket to Havana and pay in cash.
The fact that you arent supposed to be there is part of the fun. The Cubans are more than happy to have you and will not stamp your passport if its US.
Only problem is you have to carry dollars or euros as your credit cards are no good there. Upside is your dollar will get you alot farther than most of the other caribean destinations.
If you wait till relations with the US is normalized then it will be too late. We'll ruin it just like we've ruined damn near everything else in the caribean.