Can an American (USA citizen; no dual-citizenship) visit Cuba and make a video-documentary film and put it on Youtube or sell to PBS etc.?
Could some legal issues emerge? And if can, how to prevent them?
Because it will be documented on video that he visited Cuba.
Let's assume he will arrive to Cuba from Canada (and the same back).
Unfortunately there's nowhere near enough information here to be able to give a full answer for your specific situation.
Over the past few years the travel situation from the US to Cuba has changed, and there are now completely legal ways to visit Cuba as an American citizen, mainly under the "People-to-People" program which allows for "Purposeful Travel" to Cuba. The announcement of this program is available on the White House website, although the exact details of the program have varied a little since then. A number of different travel companies and organizations are offering trips under this program, ranging from National Geographic and the Smithsonian, down to individual travel agencies. Google is your best bet for finding such tours, but be sure to make sure that the organizer is licensed under the "People-to-people" program.
There have also always been exceptions to the rules for some categories of visitors, which includes journalists (although specific approval is required).
Realistically if you're look at something commercial, then the best advise would be to seek legal advice. What you're asking can definitely be done, but if you do it wrong then you could find yourself in hot water both in the US as well as in Cuba.
