I'm assuming you are referring to the late 1800's as the conquest of Native tribes in the western and northwestern United States was nearing completion.
The Canadian border, or "Big Medicine Line" as many tribes referred to it, had perhaps the largest affect on the Sioux and Nez Perce living in Montana and Idaho. These tribes were organized into bands that covered vast tracts of territory, and some of the bands lived on the American side and others on the Canadian side.
For one, the border became a sort of refuge, where natives from the US could escape out of American jurisdiction, although this did not always work. Once the conquest became complete by the 1890's, tribes were more permanently divided, and their cultures drifted apart and faded.
Though they still have a checkered past in terms of native policy, Canada did not have the westward population pressure the US did, and so their treatment of what they call the "First Nations" is generally more positive. Much of the traditionally tribal lands remained in native hands, and native languages and cultures remained relatively more intact than their American counterparts.
The U.S.-Canadian border was once called the medicine line. The Indians called it that because they believed that it seemed to have some kind of power for white men who crossed it. At one time the Iroquois nations held a strategic point located between the US and Canada aong the border.The Iroquois suffered a split in the nation as some sided with the French and other tribes sided with the British.
The Jay's Treaty in 1794 allowed the Indians to be able to cross the borders and bring goods back and forth without taxation or repercussion. The British were vacated from the forts and the french gained control of the border.