The real question now is a non US person with no relationship to the US withdrawing fiat other than USD (CAD, EUR, GBP, etc.,) to a bank outside the US. If this is also blocked then the problem is a lot more serious since this is totally outside the control of the US Government.
You really think the US Government doesn't have control over that?
Yes I do. For example Canadian Credit Cards denominated in CAD that have no affiliation with the US can be used in
Cuba.
2.) Canadian Credit Cards: Any of the "Big Five" Canadian banks are fine. Royal Bank, TD/Canada Trust, Bank of Montreal, Bank of Nova Scotia and Canadian Imperial Bank of Commerce. No problems with PC Financial or Canadian Tire Mastercards as well. And for our friends in Quebec the National Bank Mastercard and Desjardins Visa also work too.
http://www.tripadvisor.ca/Travel-g147270-c109329/Cuba:Caribbean:Money.Exchange.html