That's the way I have seen it. Song's such as "The Garden Song", by an American, Dave Mallett have ended up in those little compilations because the likes of Makem and Clancy have recorded them. But it is a part of the folk process to borrow and assume as your own, songs from other cultures. I think Archie Fisher used a Basque melody for his "Dark Eyed Molly", but I'll always regard that song as being Scottish. Eric Bogle's"No Man's Land" is usually in those books as well. I always thought it was an Irish song because I became familiar with it in pubs in Ireland. Is it a Scottish song, or an Australian song because Bogle has a dual nationality? Mind you, I wouldn't mind a bit more research when they put those songbooks together. In the case of Mallett's song, they did not even attribute authorship to him, and said that the song had come over from America.