Americans can travel there by going to another country then flying to Cuba and that has been done for years. Direct travel is more difficult. A friend of mine went for a course where he was researching marine wildlife there. His experience was rather interesting and did have its share of trouble because he is an American.No I'm not feel free to actually correct me.
But I've visited the country and seen no USA citizens and while talking to locals and learning more about the country they seem to deeply dislike you obvious due to America's constant distasteful attitude towards Communism and your pathetic failed attempt at invading them look at "Bay of Pigs incident" during the Cuban Missile Crisis and if I'm correct all this bad blood resulted in no trade and closed borders between the two I know Obama has been trying to normalize relations with Cuba though maybe this has resulted in somewhat open borders?
http://www.nytimes.com/2015/09/21/travel/cuba-vacations.html
http://time.com/money/3854538/americans-how-to-get-to-cuba/
http://www.oregonlive.com/travel/index.ssf/2015/10/cuba_opens_to_american_tourist.html
http://www.cnn.com/2015/07/17/travel/cuba-travel-feat/