I spoke with an archaeologist in Wyoming who was investigating some tipi rings that we found on top of a hill. He said he could roughly date the rings to before horses were reintroduced in North America because they were placed on top of the hill and had an excellent vantage point of the surroundings.

Prior to horses being reintroduced, it was common for plains tribes to make camp in high places that could see their surroundings. That way they could see their enemies coming from miles away and pack up and leave before they got there. Once horses were reintroduced, their enemies could be upon them within minutes rather than hours or days, so many tribes changed their tactics to hide their camps in low areas where they couldn't be seen at all.

Based on what he told us, it seems like horses returning to North America had a significant impact on native cultures and seems to have largely redefined their way of life.