late edit: DISCLAIMER: The pictured map is not actually a representation of the territories before colonisation. It's a hypothetical map of what countries there might have been had the continent not been colonised, thus all the names and borders are fictional and have never existed.
For good actual maps, check out native-land.ca.
That is exactly what happened to me. I didn't find out until I took a 23 and me test. I didn't believe the results, took the Ancestry.com test, got the exact same results. Had some interesting conversations with family after that, but basically, no one is willing to accept it's been a lie the whole time.