John Anderson My Jo -> When Johnny Came Marching Home. It might be that Ghost Riders in the Sky derives from the latter, hence the resemblance.

Hymnody was way more important in 18th/19th century Anglo-America than all other musical or verbal artforms put together. But hymn tunes didn't change very fast, and texts hardly at all (except by omission). The congregation mostly couldn't read music, but there was always somebody around who could and would keep the others straight. The same went for tunes: rural musicians kept their own tunebooks (see the Village Music Project for some) and their copies of tunes rarely varied much from the printed books they came from.

On the other hand, the way hymns were sung did change a lot, and so did the style of performance of instrumental dance tunes. Two groups of people can perform from the exact same written notes and diverge so far in their interpretation as to make the identity completely inaudible.