Much of this "cultural folklore" has some very decent historical accuracy within it.

The Khazars have done a pretty good job doing it (embracing a foreign culture/religion).

If, as some believe, the "Lost Sheep of the House of Israel" (to whom Jesus said he was sent) were the Caucasian nations of Europe and the near East, then the Christian nations might also be doing a decent job of fulfilling their (not someone else') destinies.