That might be relevant if what you said was true (it's not) or if all native Americans were descendants of the people in the Book of Mormon, or if those people in the Book of Mormon weren't destroyed.
So let's look at that:
1 - Not all Native American historians refute all of the Book of Mormon - that's impossible to claim and the truth is that most tribes have a creation story and flood story that seem to be Judeo-Christian in origin - however I don't attribute those to the Book of Mormon peoples.
For some groups in Meso-America they had specific religions traditions that actually fit very well with the Book of Mormon. Quetzalcoatl has a lot of aspects that relate to Christianity, in the Yucatan there is a temple to the descending bearded God that I've visited, and everybody knows that some of the Aztecs accepted the Spainards because they resembled the bearded white gods that were supposed to return. So you're absolutely wrong about that.
Furthermore the entire population cycle of the mid to late classic Olmec period fits the Book of Mormon text perfectly.
2 - The Book of Mormon seems to have taken place with a limited geography and mentions borders of lands, implying that other people were already in the land - therefore their religions would not have been known throughout the ancient Americas.
3 - The believers in the Book of Mormon all got killed by the group who didn't accept their traditions. It seems like some traditions (like the bearded god coming back) stuck and was passed on, but not all traditions were.
EDIT - I find it ironic that you make claims without backing them up and then come at others claiming that we have zero evidence.
What's your evidence? Do you really think that ALL non-Mormon native American historians have some evidence against Mormonism which you failed to detail or mention?
You skipped your evidence section, went straight to an impossibly difficult claim, then claim that we're the ones without evidence. Kind of ironic.
Searchery - warm fuzzies are nice, but so are facts:
The introduction to the Book of Mormon (commentary, not scripture) used the phrase "principal" not for 100 years, but from 1981 (added by McKonkie) until a few years ago when it was taken out - principal can mean "important", which was the general context most read it as.
The Book of Mormon doesn't include a single journey of people going from one end of the north land to the south part that lasts more than 39 days, and that group was lost. and it frequently mentioned the "borders of the land" - the limited geography is very much supported by the text.
The Olmec civilization has a major and abrupt end around 400 CE, it also did have a huge dip around 300 BCE - interestingly enough that is when the Jaredite group would have been wiped out - so it fits very well!
Laman and Lemuel went off with others and had brown babies, and there were large cities built in a generation - and throughout the book people identify themselves as "an actual descendant of Lehi" when according to you that would have included everybody. Furthermore there are other landings from the middle east also noted - so you're clearly wrong on there not being other people.
Quetzalcoatl isn't Jesus, yet there are Judeo-Christian elements to his legend that are impossible to ignore.
Last but not least, the land promised doesn't necessarily mean all of the land or that it's only for that group - look at the middle east, it was promised to "Abraham and his seed", that would be the Jews and Muslims. A promise like that isn't mutually exclusive against other groups.