That's not entirely true. The Iroquois were very well organized with a functioning government. The "Iroquois Influence Thesis" has been pretty well dismissed as an influence on our Founding Fathers but the fact that such a thesis could even be considered shows that there were common elements in both models of governance.
That's not to say they weren't brutal; "killed by Indians" is too common a cause of death in my family tree. Some tribes were organized and quite efficient at warfare. Disease, poor alliance choices, and military technology were greater contributors to their downfall.
You’re correct. I eluded to that point later on in the thread. You can’t treat the Indians monolithically. Some were more organized than others. The Sioux and Cheyenne were the ones who couldn’t control their younger warriors, and thus were drawn into conflicts that their elders had tried to avoid.