Folk was in vogue in the late Fifties and early Sixties, and competed with Rocknroll.
Then in 1965 Dylan walked on stage with an electric guitar, and folk and rock officially merged.
So a lot of acoustic hits by folk artists(Kingston Trio) are now heard on "oldies" stations, and hits by "folk rock" artists and "singer-songwriters" (Dylan, Joni Mitchel, Simon and Garfunkel, Gordon Lightfoot, etc) tend to be from the later era and are now heard in the mix of "classic rock stations" or "classic hit stations". But I doubt you can find a radio station that plays nothing but acoustic folk music all of the time on the FM, or AM, dial. Though there maybe some on XM, or on the Net.
Before the fall of the Berlin Wall radio fare in most Communist Bloc countries was patriotic music like marches.
In the US marches are a subset of classical music, and thus placed within classical as a radio format.
But classical has been dying out as a format.
Here in the Nation's Capital we used to have two long standing classical stations: one private and one public owned.
The private one finally went under so we only have one (though we had one little Christian station that would play religious themed operas and oratorios for a while. Don't know if it still exists).