Based on what I personally think is correct (please correct me if you think I'm wrong ), I doubt theres many public domain spaghettis in USA either. I know this has been the subject of lots of discussions on several boards over the years so people are probably tired and annoyed of hearing about it, but anyways... xD
USA joined the Berne Convention in 1989 but refused to give the proper copyrights to foreign works that had been released before they joined. But in 1994 Clinton signed (under pressure from other countries?) URAA which basically automatically restores copyrights to foreign works that are still copyrighted in their country of origin. Even to those which had fallen to public domain because of failing to follow the US copyright laws.
They Call Me Trinity is probably the most famous of the public domain titles, but the US copyright office actually has a 'notice of intent to enforce the restored copyrights" from Enzo Barboni (his name is listed as the copyright holder if I remember correctly) and/or his people left in 1996.
It would probably take some court cases to see how the laws actually would be enforced (if at all), so I'm not sure if anybody can actually say what the situation is.
I do know about one court case in which a distributor of previously public domain foreign works (music) was ordered to stop what they were doing.
But I think it was possible to get your own copyright on the modified works from public domain titles by for example changing the title card or music or something. I recall hearing about some cases like this, maybe one was plan 9 from outer space which is public domain but certain version/print (maybe the best around, hehe) is copyrighted to someone else because they changed the titles... or something.
So maybe some of the crappy vhs versions (made before 1994) aren't actually copyrighted because of some possible modifications... but then again, I would think the one who made the modifications own the copyrights for that version, maybe it would even be considered made in USA after that and not foreign.
As for your short film Morgan Kane, I doubt the copyright owners would care about a short film that isn't made with an intention to make loads of money with it.
But who knows... ???
17 USC 104A effectively restored the copyrights on foreign works that previously were not copyrighted in the U.S. due to a failure to meet the U.S. formalities (such as not having a copyright notice, or not having been registered with the U.S. Copyright Office, or not having had its copyright renewed) or due to a lack of international treaties between the U.S. and the country of origin of the work. Copyrights on foreign works were only restored if these works were still covered by copyright or neighbouring rights in their source countries on January 1, 1996. But if so, the copyright in the U.S. was restored automatically; the restored copyright is subject to the normal U.S. term as if the work had never fallen into the public domain in the U.S. (104A(a)(1)(B)).