I have found that since I grew up loving both blues as well as country music simultaneously, I really didn't see nor hear any great divide between the two. In many respects old country was really "white blues" and the influence of black blues musicians was so easily absorbed by the whites who may've been physically segregated from the blacks, but who still picked up on what they created with their musical language.

If you listen to the great Jimmie Rodgers, Roy Acuff or any of the other early, early country stars it's easy to see the blend of blues and country that made this sound so universal. The I-IV-V was still the preferred chord progression, but also the "ragtime" progressions started to take hold as well.

This was equally prevalent in black as well as white music, and took hold in the "Roaring '20s" when Jazz also started to become a true American phenomenon. If you look at it, Jazz is really the ultimate hybrid of all these styles, and the earliest forms were structured so much like blues as well as country, and seem to just "take it all in" in a musical, as well as cultural sense!