I think it was mostly a case of "benign neglect" in Canada rather than extermination. There were very few Indian wars in Canada following, of course, the extensive fighting that occurred in the French and Indian War that preceded the American Revolution.

During the same period, there were hundreds of Indian wars in the USA. The British government, on the whole, appears to have been intent on avoiding such conflicts, but it had the advantage of sending in the legal apparatus first into new territories, rather than allowing settlement first...with little or no law. It was the aggressive expansion of unregulated settlement, whiskey-trading, and other essentially "free market capitalist" policies that provoked most of the Indian wars in the USA. The indians, in essence, were sitting on precious land and resources that the settlers and business people wanted to exploit...so the Indians had to go.

In Canada, the crown went in first (in the form of the mounted police) and established the rule of law. Then settlers came in afterward. There was no lawless period in the territories, and whisky traders were not allowed to set up their operations. This greatly assisted in maintaining peace between Whites and Indians, because the law was there and the law was not to be questioned, and everyone understood how it worked, Indians included. It greatly protected the Indians from the worst abuses, such as the whisky traders and lawless men and gangs that terrorized the American West during the same period...a period of almost unbroken peace in the Canadian west (save for the Riel rebellion).

The British approach was essentially a socialist approach, in that the central government goes in first with police and courts and legal systems, and establishes the rule of law.

And that basic difference in national philosophy between the USA and Canada remains to this day. The USA has always encouraged unregulated laissez-faire aggressive profit-oriented business operations by private commerce of every sort to open up any new area that is annexed. Making money becomes the main motivator. The British back then brought in the rule of law first, and business afterward. That's a vital difference in social philosophy. What are you really in it for? Establishing social order? Or making a quick financial killing and getting something for nothing? In the American West, it was the latter, and that's what caused most of the Indian wars to occur. The Indians were getting robbed everywhere the USA settlers went, they had no legal recourse of any sort in the lawless territories, so they fought back with every means at their command. In the end, of course, they lost. And the Indians lost in Canada too in the end....but not in nearly so violent a manner.