Americans are not allowed to visit Cuba because MiamiCuban exiles don't want Americans there. The exiles can fly directly from Miami or NY or LA to Havana, and also can fly their Cuban relatives from the island to the US for visits - so they have exactly what they want until Castro is gone, and they think they can take over Cuba!
The WH and US State Dept. will do anything the exiles want, because they provide almost a million votes and lots of campaign $$$ to pandering politicians.
The following article shows how B* is kissing Miami butt to try and get those million (mostly republican) votes!
Notice how Homeland Security is used against Americans freedom so B* can curry favor with MiamiCubanos!!!
snippet:
Bush has already strengthened measures to identify and fine U.S. citizens who travel to Cuba illegally through third countries; the Department of Homeland Security has trained hundreds of Customs agents to spot illegal tourists at airports across the Caribbean and in Canada, the paper said.
http://quote.bloomberg.com/apps/news?pid=10000086&sid=aPxpxJN6wcUo&refer=latin_america