In the ancient past, small horses did range the west, but these have long been extinct. The Conquistadores brought the present horse. But soon the Indians of the Plains did become some of the greatest horsemen the world has ever seen. They Sang for Horses, by LaVerne Harrell Clark. It is not possible for 20th Century technologically-dependent people to grasp the achievements of early Indians.
Indian architecture is unexcelled.
Indians' perception of the relations of the stars created their extremely accurate calendar. They used the zero in mathematics before it was discovered by the Arabs. Six hundred years of recorded Peace gave the Aztec and Mayan peoples leisure for experimentation and communication of ideas. This all came to an end in the 16th century. Although Indians have title to some land, they are not allowed to administer that land.