We have a fictional somewhat antagonistic male unseen character whose last name begins with S, likely created between 1950-1960, and neither originally from prose, TV, movies, theater, and comics, nor adapted into prose, TV, movies, theater, and comics. We’ve ruled out children’s songs but not songs in general, or–if it’s not covered by TV–advertizing.
Also the interestingly ambigous “American among other” creators suggests something that arose culturally rather than being designed. So something sort of meme-like but from around the 50’s.
So he’s something of an antagonist, so maybe he took somebodies girl or is in some way acting as an obstruction.
The time of creation and the creator is somewhat ambiguous so it could be a folk song.
Unfortunately since I started wracking my brains for song S last names I have “Mr. Sandman”, who fails at least 4 of the criteria, running through my brain non-stop.
Its not originally from theater which I think would probably rule that out. Also a musical would probably having a well defined creation date and author nationality.