Most First Nations worldviews hold that no person "owns" the land. Instead, there is a more common belief in stewardship of the land. It is the duty of humans to act responsibly with their actions so as not to disrupt the natural flow of life. The land and the environment are part of one big picture, and it is morally wrong for humans to do things which dominate over the other parts of nature.
Unfortunately, Europeans who encountered First Nations people did not have the same opinion. During the time Europeans were beginning to travel to the Americas, ownership of land was a hot topic. Much of Europe operated on some form of a feudal system, where all the land in a nation belonged to the king or prince and was divided under the care of nobles in return for military service. These noble houses further divided the land into the hands of vassals, who then hired peasants to live on and work the land. Such a complex system oppressed many while benefiting few, and a significant portion of the population lived under the illusion that they "owned" the land they lived on when they had no real power over it. This class inequality and lack of agency was the motivation for many a revolution.
In general, most Europeans believed that land could, and should, be owned by someone and worked to benefit the people. Note that this working of the land offered the most benefit for people at the top of the social hierarchy, and the least for those at the bottom. In most First Nations belief systems, owning the land is not possible, and any interaction with the land should not be for the sole benefit of humans- especially at the expense of others.