I propose there is a great yearning in this country for something like "religion" or "patriotism" that everyone can accept. Then I will propose that the impulse is to make "Indianizm" into that principle. America embraces both the peaceful, protected idea of the Wise Old Person who has special insight into the world, and also the superhuman violence of those outside the culture who endanger it. The two make an oxymoron that is very satisfying for many people.
The trouble is that most people wouldn't know an Indian if one hit him in the head with a Dream Catcher. What most people -- and even many Indians -- think they know is something the movies distilled from reality. Edward Said woke up a lot of people with his book about "Orientalism", the combining of a few sensational characteristics into an imaginary culture which hypnotized us all in print long before movies. Every race seems to have this tendency to pick out their fav elements and compose them into an unreasonable facsimile of some glamorized group.
My Twitter account includes a lot of indigenous people in all their variety as they developed within the context of a specific ecology. Salmon or bison, corn or rice, seal or moose, each place produces a particular culture and, given enough time, can standardize their genomes enough to justify saying they are a tribe or race. But the only real shared organic thing is that their genomes developed from people who crossed the Pacific instead of the Atlantic. Or maybe the Arctic Ocean. Therefore, in the American army indigenous soldiers could often "pass" as Chinese or Korean. Very useful. Saved lives. Not just the Code Speakers.
But on my Twitter, many are trying to solidify their identity in terms of tribe and define that in terms of social rules as well as material culture. They get upset when something developed by one tribe is adopted by another. A fascinating book is "The Hako: A Pawnee Ceremony" by Alice C. Fletcher 1838 -1923(Author), James R Murie (Author), Edwin S Tracy (Author). Few know this amazing idea about the development and adoption of the long stemmed pipe and its ceremonies. Another book in this mode is "The Shape of the Liturgy" by Dom Gregory Dix which is the similar history of the Mass and how it changed, passed along to the next group and augmented as it went. The missionizing went both ways.
But to many people with the notion that a religion is something true, unchanging, and recognizable from outside, none of this is admissible. To them "Turtle Island" is as valid as the fanciful idea of the planet balancing on an elephant standing on a turtle. Impossibly, people want to do the One Right Thing, and be recognized for it. They look at someone whom they think looks "Indian" and ask, "Are you Indian?" If that person says they are not, they say, "Oh, I know you have to stay disguised." They insist.
A claim to being American is knowing an "Indian." One rather humorous expert suggested that we each live within 9 miles of an Indian if you count all those people with Cherokee grandmothers. In Vietnam anyone who was Indian was believed to have superhuman sensitivity as in romantic novels and were made to walk at the head of columns as a protection, though they may have grown up in Chicago or even a nice suburb in California. Anyone with even a suggestive or playful claim can be pressed to BE an Indian. In one setting it's an advantage (a bookstore) and in another (a county seat next to a rez) it can be a hazard. Best to keep feathers out of one's hair.
Some of this is the remnant of German nature idealism, which insists that the untouched primeval world and the innocent newborn baby are sacred carriers of what is natural and therefore true.
Some of it is undoubtedly guilt over what is done to the original inhabitants of this continent. Some of it is provoked by the slipperiness of who is and who is not enrolled since they may be cousins with one percentage point difference. One can't count on tribal certification or even genomic charts, since by now most people are mixed and most tribal people resist being analyzed, so there aren't enough examples to identify a plurality of gene clusters.
Everything alive is connected. Everything alive is changing. What was an "Indian" yesterday is something different today, but still "Indian." Some ideas about Indians come straight from slavery when a person's identity made them objects for sale or "free men." So the tiniest percentage of "black" blood made a person available for owning, even a president's wife/slave. (Actually, the two states are related.) Metiz could not exist before white contact, but now the Western metiz mixed with English or Scots are splitting from the French-mix metiz, which is esp tricky since many Indian people pretended to be French in order to escape dangerous prejudice.
This is necessary furor and indignation, in order to get ourselves in true communication, but it should never expand to harm people. We are all human, all animals, all mammals. We all have red blood.