This is an old debate. George Pullen Jackson argued that black gospel was European in origin, and in turn he was challenged by scholars who insisted it was African-American in origin. To my ears, it clearly is a hybrid form: A New World form derived from Old World antecedents. In that way, it's like most American folk music (unsurprisingly so). The parallels between gospel and some Hebridean forms have been noted more recently by Robert Cantwell in his book on bluegrass, though he argues strongly (and convincingly, I believe) for cross-fertilization between British and African forms in American music. He even uses the dreaded "C" word

I think there is a problem in framing the argument upon a search for ultimate sources. National folk song forms and styles do not exist as discrete entities, and isolating one influence to the exclusion of others is bound to lead to problems.