There's a discussion going on in one of the ADF mailing lists about honoring the spirits of a place and how that can intersect with the beliefs and practices of Native American tribes that currently or formerly live and worship in the area. It's an interesting discussion, though somewhat lacking in perspective because of the closed nature of the group it's taking place in.
I think it's important to at least make an effort to research the mythology of the area where you live if you're trying to form a relationship with the land. After all, some of the land spirits are going to be the same ones that others have worshiped for a long time. The Columbia River was here long before white folks showed up, and I do my best to honor that.
At the same time, I'm not Chinook or Kalapuya or anything even close. I can try to reach out to local spirits and gods, but I'll be honest... I'd be hesitant to write in-depth about working with gods known to the local tribes, even if I did have a relationship with them. Native mythology is still widely ignored or misunderstood, and I wouldn't want to risk contributing to that. (Virtually every website I've seen that talks about Quileute mythology, for example, has a nice bold note that there are no Cold Ones in Quileute myth and can everyone please shut up about Twilight already. Because people read things and they believe it.)
There is definitely a point where you can go too far. Attempting to recreate Native American rituals in any way is probably crossing it if you haven't actually been trained in that kind of thing. And I think we all know a plastic shaman when we see one at this point and know not to touch that shit with a ten foot pole.
My goal, in the long run, is to build a religious practice that's intensely local: working with the Columbia and the Willamette rivers, with Portlandia and the Skidmore Fates, with the bridges and the nearby mountains and the Pacific Ocean and on and on. While some of these spirits are obviously considerably younger by deity standards, some of them have been here for a very long time and to ignore that is to do them, and my relationship with them, a disservice.