Do you believe they are truly comparable scenarios (warring tribes vs. colonialms)? Is there really no difference in the quantity or quality of suffering between the two cases?

Why are you trying to "compare the quantity or quality of suffering"? This isn't a game where we get high scores. Warfare is a constant in human history. Conquest, subjugation, rape, enslavement; these are things we see in the past in every region where we have records. The only places without record of such horrific past are places without records. You are claiming "unique among all humans, Indigenous Americans lived in this place for 15,000+ years without the land changing hands violently." That is a claim I do not believe, and there is no source provided by you. This is an extraordinary claim and so far the only evidence supporting it I've been given is the racist stereotype of the "noble savage", where the Americas were a "garden of eden" where people did not engage in these practices until the introduction of sin by the Europeans. This is a racist fantasy.

Where do you draw the line of "acceptable" conflict? Was all European colonialism A-ok in your view, or do you think certain aspects of it were immoral? How about things like the slave trade, King Leopold's Congo, the Rape of Nanking, the Holocaust, the bombing of Hiroshima and Nagasaki, etc.? Surely there must be some line that goes beyond what you consider "acceptable"?

I am not defending slavery, warfare, rape, conquest; that is YOUR position. You are the one claiming that the slavery, warfare, rape, and conquest practiced by Indigenous Americans against other Indigenous Americans didn't occur. This is really an insane thing to say.