Gentlemen, one thing you must remember, and I'm not sure that anyone really wanted to bring this up, but these whole Indian Wars was the result of a deliberate campaign of deportation and genocide. Little Bighorn might have been a military victory, but Custer and his men finished the attack and burned their tents, killed many of their women and children and, to put it simply, crushed the Sioux so that they would never recover. THERE WOULD BE NO PRESIDENT CUSTER--He was only a colonel at the time of the fighting, to suggest just how ASB this whole six star thing would be. There has, to this day, not been a six star general.
Now that we have this straightened up--the answer is no. The Reservation System was abusive and mean-spirited to be sure, but even that concession was only made under FDR in the early 1930s. Recall, that in the Spanish War, the USA deployed Chain Guns against Spain, which quickly folded against the US Army. The Sioux might have a few guns and many skilled warriors, but try taking on machine guns. The US Army didn't even treat the natives like humans--they can and will shoot prisoners, or kill non-combatants.
So Little Bighorn, even if it doesn't draw a massive US response, is likely to one victory in a saga of destruction for the natives. The Sioux have no way out in the long term--Recall that Chief Joseph attempted to flee from the United States but was intercepted by Federal Cavalry. How ASB are we getting here? The USA, far back in its history, used biological weapons against the Natives. If the USA gets chemical weapons they'd use them too. Don't forget that whole tribes of natives were killed over small bounties. To put it bluntly, Hitler didn't invent the idea of Living Space, or his deportation or extermination of "lesser races".
Seriously, the Sioux are doomed as soon as Richmond Falls. Whether that takes machine guns or chemical weapons might be a testament to their resilience and the fact that should they loose they can expect a hangmans noosing or a death squad should they fail. Regrettably, I think they are going to do exactly that.
The USA has done its share of depraved, evil things and the whole treatment of Indians is pretty National Socialist. It pains me to think about it but its worse to deny it happened.