I would probably say it's both. I would hear it on some of the less poppy country stations at the time and on some of the same 'classic rock' stations that would play more Southern rock like Lynyrd Skynyrd.
Earle himself calls it the world's first blend of heavy metal and bluegrass, and the January 26, 1989 review of the album by Rolling Stonesuggested that the style be called "power twang".
Remember that at the time Steve was partying with Guns ‘n Roses and living hard.
Not sure it's either....as mentioned....it's sort of Steve Earle doing his thing.
Saw him play in London way back. It was interesting, the crowd came for Copperhead Road, they were pretty lackluster for most of the show. He then bemoaned having to play Copperhead road and begrudgingly did it, at which point, everyone cheered and then left. Seriously, the place emptied out halfway through his gig. Weird. Although I saw the same happen to Billy Ray Cyrus and Achy Breaky Heart in the same venue! At least he waited till the first encore.