Great, so simply acknowledge that it is <ythic rather than historical, and that while some native American cultures have inspired certain elements that a European worldview prevails as it is part of the Ars magica setting.
If you have ever read the Lord Darcy series they do something similar with their "alternate" native American civilizations, although in that world Meso-American civilizations found real power in blood magic which resulted in significant alterations... the main point is to have something to point to other than authenticity as the goal and have it be very clear that you are not trying to be authentic. Changing the spelling of tribal names and such also tends to help...
I don't think that'd be defense enough. Monte Cook Games is a pretty sensitive shop, and their recursion in The Strange, while it aggregated a lot of elements together, was only like a 500 word entry and they were taken to the woodshed for it. I do this out of love, and I don't want to draw that kind of fire.
It'll need to wait for a while, at least for me. I don't have the bandwidth to do it for a bit, and I'm inclined to try getting a different ArM5 project off the ground first.