This created wars and battles. If you own a tribe in Arizona, and the Pequots from CT showed up at your front door, to hunt your food, use your land, and eat your berries for 5 months - I can imagine a violent confrontation.
Plus someone else (those pesky white guys! or another tribe) can easily move in and take your land while you're gone. Too much at risk.
Yes, it did, but those wars rarely caused death. Most inter-tribal battles were honor based (i.e., counting coup). Native Americans had a very complex system of barter. They were not opportunistic, ruthless murderers, they were not ignorant, and they had a system for communicating between people who spoke different languages. They generally tried to work things out in amicable fashion through trade, marriage, etc.
Excluding the Magna Carta, the Iroquois Constitution is the longest-existing international constitution in the world. This was an orally transmitted constitution which describes a union of five (eventually six) Indian nations: Mohawk, Onondagam Seneca, Oneida, Cayuga and the Tscarora, which was adopted around 1715 and which the framers of our own constitution drew from quite heavily.
Be that as it may, the fact of the matter is that it is virtually impossible for hunter/gatherers to live side by side with an agrarian culture. The two lifestyles are utterly incompatible.