Did the Native Americans believe in monotheism, or did they live on polytheism before the discovery of the Americas?

We are not aware of the religion of the Native Americans before their discovery. However, the noble verse, "And We would not punish until We send a messenger," means that Allah does not punish anyone until proof is established against them by sending messengers and the message reaching them. If the message of the prophets did not reach them, then their ruling is like that of the people of the fatrah (interval) who will be tested on the Day of Judgment.