Northern Plains...
Allies of the US...Shoshone, Ute, Ree, Pawnee, Bannock, Nez Pierce, Crow, Osage, Kaw, Winnebagos, and many smaller tribes such as the Poncas, Otoes, Peorias, Omahs, Mandans.
Southern Plains..
Allies of the US ...
Caddos, Anadarkos, Wacos, Tawakonis, Tonkawas and many more smaller tribes.
We did have a few fights with our allies from time to time. The Nez Pierce and Utes comes to mind.
The Nez Perce story is a particularly sad one given that they tried their best to stay at peace with the white man. I have been to Bears Paw battlefield in Montana where Chief Joseph was forced to surrender—very evocative lonely place. A distant relative supposedly had the grave of Old Joseph on his farm in Oregon but was careful not to cultivate the burial site—when he was growing old he arranged to have the grave moved. But there is some doubt whether it really was Old Joseph’s grave. The US government’s treatment of Chief Joseph after his surrender was outrageous.