And he borrowed heavily from the pseudo histories of the time. I didn't mention Nazis did I? It was relatively common in the preceding era to build notions of where the Europeans came from that pointed north, and you can map that material onto it quite easily. To suggest nobody has ever drawn a link there is nonsense but it is not drawn out very often. Mostly because those histories are now gathering dust and were entirely fictional constructs but they can still be glimpsed in folk tales and in fantasy novels of today with a line drawn through Howard's world building. Also becuse to draw out the similarities is an uncomfortable reminder of an era gone by, just as many pulp novels are.
I can't imagine any of the more academic writers in comics not addressing this in some way, and that may be where issues arise.