Regarding "This Land", not all people from urbanized communities fed on piped in pop music will know this song but it continues to be circulated in other environments and in this instance, I mean this respectfully, it has been around with variants for some time as Woody would have wanted it to be and of course reality is in the eye of the beholder.

I think - and I mean this respectfully - that there's 3000 miles of ocean between a lot of us here and the country Woody Guthrie was writing in and about. I'd never heard "This land" until I encountered the Internet.

Several of your other examples fall into the dreaded 1954 Definition without any trouble at all - few if any collectors believed that all folk songs were composed collectively or anonymously and preserved only within the oral tradition.

Defining "folk song" is a fool's errand - some "folk songs" are only found in one variant; some are found on multiple broadsides but without any variation; some are found on broadsides and don't appear in the oral tradition at all... Personally I'm happy to say that "folk songs" = "all the songs collected by folk song collectors, with a few completely subjective exceptions and additions" and leave it at that. It's not as if we're going to risk running out of folk songs if we define them too narrowly, after all.