Had Custer won at the Little Big Horn, the battle today would simply be relegated to a footnote in the Indian wars and soon forgotten like many bigger battles.
This would mean that THE WASHITA battle would also have been nothing but a little “dust-up” on the High Plains, and without Black Kettle being killed there, Sand Creek would also have been forgotten. Black Kettle’s band was instigated to fight by Confederate Agents in the tribe.
Just for the record, during 1868, at the Washita, the Cheyenne and Arapaho were NOT on their reservation, but almost 90 miles SW of there. their reservation at that time was East and north of the Cimarrron River, West of the Arkansas river and South of the Kansas line. The old former Cherokee strip.
Instead, they were camped on the Washita, in the former Choktaw-Chikasaw lands.
They were not given the Washita area till several years later.
I take your general point but the Little Bighorn would have been more than a footnote even had Custer won. Custer encountered the largest assemblage of hostiles in the history of plains warfare, and probably Indian warfare generally north of Mexico. The battle was a black swan event. Plains Indians did not travel in groups of 7- 10,000 people. They lived by hunting and had to disperse to find adequate game. A couple of hundred people would have been a very large village. Most were smaller. In this case, the Indians had concentrated to fight Crook on the Rosebud and had not yet scattered. Custer showed up at an unlucky time. His decisions make a lot more sense if one remembers that he was encountering something outside any normal frame of reference. A cavalry regiment should have been more than a match for anything it was likely to engage.