Well one thing to learn would be to not make a circular firing squad.
Quite true.
I always find it interesting that the few times the US Army arguably engaged in atrocities, such as Washita and Wounded Knee, are constantly being tossed out to show how immoral and illegimate the US is.
Meanwhile, atrocity was the normal method of Indian warfare, it’s what they did. So it could be posited that Army doing the same was just being culturally sensitive, imitating the culture of the natives.
At its very worst, the Army never captured Indians and dragged them off for long slow death by torture, which was of course standard practive for most tribes when they got the chance.