Bob Dylan either goes to Sun Records and revitalizes the label, or else he records under Holly. Either way, he doesn't write most of the early '60s songs he's most famous OTL for, doesn't need to go electric at the Monterey Pop Festival (since he probably already is) and isn't credited with inventing Folk Rock, Neil Young is.
When Buddy Holly goes country sometime in 1960, as his diary seems to indicate he woould, this would alienate much of the Liverpool "Merseybeat" scene, causing most of those who stayed in music to turn to skiffle in spite, making them unapproachable on this side of the pond, thus aborting roughly 2/3 of the British Invasion, including The Beatles, as well as the Merseybeats, the Hollies, and the Moles. Of course, the London Based Blues Rock scene of The Rolling Stones, The Who, The Yardbirds, Peter Green era Fleetwood Mac, and Ten Years After will as a result do that much better without the competition. With no first few hits for the Stones written by Lennon and McCartney, they would have gone straight for "Satisfaction."
Whether or not Holly can manage a band to become a "Stray Cats twenty years or so early," there may or may not be Psychobilly twenty-five or so years early.
Holly will eventually get involved with either the Austin or else Bakersfield country scenes. If anything, either California Country Rock will be known in the mainstream for more than just The Grateful Dead's country years and The Eagles, or else Southern Rock will be even bigger and last longer than OTL, though I do wonder what Holly would have had to say about the 90s' "Young Country" of Garth Brooks, Wade Hayes, and Billy Ray Cyrus.