Which Native Americans historically have said they used to hunt them? Mammoths went extinct in the USA around 12000 years ago, so this story doesn't ring true. Oral history just does not survive that long
There's a debate as to whether giant animals from Native American folklore are a warped cultural retention of extinct megafauna, sure.
To be clear, Native Americans did hunt Mammoths, and they have also been oppressed and culturally maligned. No disagreement there
But I'm very much questioning that Native Americans outside of modern academic contexts have claimed knowledge of what their tribes hunted in 10,000 BC