In order, they are Cherokee (730,000), by three lengths, Navajo second, and all in a bunch for third place (170,000), Indians from South of the Border, Choctaw, Chippewa and Sioux.
The Navajo and the Hopi have been competitive tribes for centuries. The Navajo now outnumber the Hopi by 25 to 1. The Hopi may have become more integrated in the general population, they have a reputation for being very adaptive and they look more Asian. The also have a reputation, like Arabs, of saying whatever the listener wants to hear to make reality conform to saving face.