I don't remember anything about "hard feelings over the whole Independence thing" from either the British or Canadians, I've only heard that from Americans.
"The United States declared war for several reasons, including trade restrictions brought about by the British war with France, the impressment of as many as 10,000 American merchant sailors into the Royal Navy, British support for Native American tribes fighting American settlers on the frontier, outrage over insults to national honor during the Chesapeake–Leopard Affair, and American interest in annexing British territory, and expanding the United States further north" https://en.wikipedia.org/wiki/War_of_1812
"In the early months of 1812, as tension with Britain increased, President of the United States James Madison and Secretary of War William Eustis were urged by many people, including William Hull, Governor of the Michigan Territory, to form an army which would secure the former Northwest Territory against Native Americans incited to take arms against the United States by British agents and fur trading companies. In particular it was urgently necessary to reinforce the outpost of Detroit, which had a population of 800 but a peacetime garrison of only 120 soldiers. It was also suggested that this army might invade the western districts of Upper Canada, where support might be expected from the many recent immigrants from the United States who had been attracted by generous land grants" https://en.wikipedia.org/wiki/Siege_of_Detroit