I think that was probably the radio program I heard that talked about why American country music was going to be popular around the world for a long time. So much of the developed and developing world has people who used to live on the farm, or their parents or grandparents did, but they’ve moved away from their roots to the big city, far from the beautiful countryside they remember (and the hard grinding poverty of subsistence farming that made them leave, though that’s also in a lot of those songs.)
And a lot of John Denver’s music, and country music in general, is easy to sing, easy to play on a guitar, just “Three Chords and the Truth”, but enough depth and complexity in some of the melodies and harmonies to make it still worthwhile.