I had listened to some of the old blues masters and had a hard time "finding my way in" to the music. I remember particularly picking up some Lightnin Hopkins albums on folkways that I never really connected with until I began listening to some of the British youngsters translate the music to my pop sensibilities - from there it was a slam dunk.
I think bands like Canned Heat (though they were American, I know), Fleetwood Mac and even John Mayall did a good job of adjusting our ears to the real thing. Other Americans like Spider John Koerner, Dave Ray and Tony Glover also helped, for me at least.
One of my favorite live blues memories goes back to New Years Eve 1968. I saw Muddy Waters and Fleetwood Mac (with Peter Green) at the Kinetic Playground in Chicago. Muddy was electric and unbelievable. Fleetwood Mac did "Yer Blues" and slayed me.
The kicker to the night, though, was the closing act - The Byrds, with Clarence White. After 3 hours of the best in blues, I was astounded by the way those guys played country (which I had always hated). I heard Roger McGuinn do "Old Blue" with finger-picks and I was hooked. That led to twenty-odd years (some extremely odd) following a path back to Hank Williams, Jimmie Rogersm, Merle Haggard and Lefty Frizzell - but that's another story. . .

Oh yeah - the First ZEP and The Blues Breakers w/John Mayall are still two of my favorite electric blues albums.