When the sanction ends, hopefully it will be possible to use a US issued bank card in Cuba.
EDIT:
saw this in
WSJ Blog:
Travel restrictions
It will still be illegal for Americans to travel to Cuba strictly for tourism, since that is banned by federal law. But U.S. law allows for 12 categories of legal travel to Cuba, which the Obama administration is expanding.
The allowed travel categories are: family visits, government business, journalism, professional research and meetings, educational activities, religious activities, “support for the Cuban people,” humanitarian projects, private foundation work and research, import/export work, art and athletic performances, clinics and workshops and other export transactions.