As the bison were a huge staple of native American life I find it strange that native Americans weren't farming them and using them as pack animals before the Europeans arrived. I'm not sure if the the bison would be as easy to tame for the the native Americans as it was for the eurasians to tame the aurochs
This isn't really a question for the Historians' subreddit. This would be better off in /r/AskAnthropology, and, as it turns out, it has been asked many times there. Here is an example thread from over there.
This question has been asked several times on r/AskHistorians and received a number of answers.
https://www.reddit.com/r/AskHistorians/comments/w9v9j/why_didnt_the_plains_indians_try_to_tame_the/
https://www.reddit.com/r/AskHistorians/comments/44jhh9/american_indians_domesticating_bison/