I mean, wow! /sarcasm/ If you want a supernatural mystery, it has to have something to do with the marginalized Native peoples of that land, and the white protagonist just has to ask the nearest Native what's going on to be told What Is Going On And Why, and maybe what the solution is! The solution never is "Get your white asses off our land," amazingly.
Throw into the mix some set of stereotypes about the Native people of that region, toss in that the author is writing this story because he or she wants to honor these people or finds them fascinating (though it never seems that these authors had much contact with these people irl, other than living nearby at most), and make sure that the story is really about white people in the end (with some Native "seasoning"), and bake on high for two hours.
I'm not sure how to take this issue on more effectively. In simply weeding it all out, I'm also weeding out mention of peoples who never get mentioned in SF. But if what's said about them is wholly or mostly inaccurate, then I can't let that go through, either. (I'm not an anthropologist, I just know how to use Google, and it usually takes me under five minutes to find several major issues.)
The real solution, of course, is more Native authors. In the meantime, and in parallel with that goal, though, what else can I do? How can I handle this issue better? I already have some stuff up about it on the guidelines, but that doesn't seem to be having much visible effect. I also don't like "speaking for" Native people in saying it's inaccurate, even though it is inaccurate and the authors admit they made it up.
 I take personal issue at the use of the term "creative license" to describe this behavior. These authors have no legitimate license of any sort to invent the beliefs, customs and traditions of real life groups of people. No license of any sort has ever been, or ever will be, granted. This is fraud and theft, and sometimes it rises to libel. They have no "right" to do this other than the right they gave themselves, and the "right" accorded them by majority privilege.