I have no doubt there was violent conflict between tribes. I don't wear rose coloured glasses. Prior to Columbus though, most tribes, particularly on the East Coast were agrarian (read 1491) and almost all tribes were engaged in some form of agriculture throughout the Americas. Many of the "civilized" cultures, like the Aztec and Incas were rather brutal. But after 1492, up to 90% of all peoples were killed by disease and guns (the Spanish were particularly brutal) forcing most tribes to become hunter/gatherers again, and as settlement began, tribes were being displaced and forced from their territories which escalated violent conflict.
I am also aware that humans, in general, are war like and our history on this planet has been one of massive bloodshed. But it is also known that the very first European settlements on this continent would have perished if it had not been for the aboriginal people helping them. Their reasons for helping the settlers may not have been totally benevolent, that is for sure.
And yes, the Cree were nasty to the Inuit but if you know the history of the Inuit, you will see that part of the motivation of the Cree was that the Inuit wiped out every tribe they came across when they invaded the north from Siberia a thousand years ago. They even wiped out the Norsemen on Greenland and we all know their reputation for being war like.
Somewhere between the European and aboriginal version of what happened at the first harvest feast that settlers and aboriginal peoples shared, lies the truth. I just think there may not have been a first harvest if the aboriginal people had not shared with the settlers their agricultural expertise of what would grow in that climate.