Actually, it was the logistics, as it always is. They were subsistence hunters tied to family groups. They didn't have the ability to leave the families behind and fight for extended periods without having to hunt. This combined with numbers, limited water (which made it relatively easy to know where they would go) and superior firpower and resupply made it game over. Becoming dependenton the enemies weapons didn't help all that much, but they used what they got well.
FQ13
Much of what you say may be true of the western indians, but it does not apply to the Eastern tribes.
Water was readily available , as far west as the Mississippi basin they lived in established towns , relying on tended crops just like the European settlers, and the single shot muzzle loader actually was inferior in rate of fire to the bow, while it may have given some advantage in range this was largely negated by the forests where most fighting took place.
The Three things that defeated the Eastern tribes, and set the stage for the defeat of all tribes were:
1 - Inability to work together, the individual tribes put their own interests ahead of the interests of the whole, often supplying help to the Whites against an ancestral foe only to later become victims themselves.
2 - Dependance on trade for things they could not supply themselves, For example, during the 150 years between Plymouth Rock and the Revolution many natives gave up the bow in favor of the rifle, with the defeats of their French, and later, British allies they became dependent on the US Gov. for their supplies of powder and shot, at the same time their skill with the bow declined, therefore when their powder ran out they no longer could war, but their ability to hunt was also degraded.
3 - Individual discipline, Trained soldiers will ALWAYS defeat warriors in any but single combat. Warriors fight as a group of single fighters for personal glory, soldiers on the other hand fight as part of a mutually supporting unit, while the warrior may be the better of any single soldier, while he is proving it the rest of the unit is moving to isolate and overwhelm him.