I suspect the music they're playing is a mixture. I tend to think of Cajun as white music with African American influences and Zydeco as AA music with white influences, but being British I'm probably wrong about that. I know Christine Balfa (Dirk's wife) is the daughter of Dewey Balfa, the late great Cajun fiddler, some of the others were zydeco players. As to their politics, I'm afraid I couldn't hazard a guess, but the people in the film seemed to be cheerfully Democrat.

Cheers
Ray