Thanks for the further info. One of the articles linked to in the first one states that he is a U.S. citizen, so that's cleared up.
I still think "U.S. man of Cuban origin" is ambiguous on the face of it, though, and would have some misgivings about rendering it with "US-Amerikaner (kubanischer Abstammung)." I still maintain that you could say "U.S. man of Cuban origin" about a permanent or long-term U.S. resident or naturalized U.S. citizen born in Cuba or elsewhere to Cuban parents. That's a whole lot of room for different circumstances.
Simply calling the subject "an American man" seems a bit off, although he was actually born in Puerto Rico. Journalists often solve these kinds of problems by identifying the person as a "U.S. national" or "U.S. citizen" – which is exactly what MSNBC did:http://www.msnbc.msn.com/id/40910997/ns/us_ne...
What have the German papers done with similar headlines that are meant to point out that a person holds the citizenship, but for whatever reason doesn't seem to be identifiable as a member of that society, like the ones about British or U.S. citizens of South Asian or Middle Eastern origin/extraction (often prefixed "X-born") who have faced terror charges?