I know Willie Dixon gets credit for a song on Led Zepplin I. The lyrics and tunes would have to be practically identical to win a plagerism case for a 12 bar blues. Thousands of people using the same few chord progression's and the same few themes for what? about 70 years now?

I don't know about "caucasian" tunes and words. Aren't East Indian, Arabs, Italians and Scandinavians also caucasians. We don't exactly all have common music or poetry. Jimmy Page had someone to copy. So did Muddy Waters (though maybe Muddy had more people copy him). Music is music and people are people. Race is irrelevent.