If the majority of voters in a Canadian province vote to secede and join the United States, then the US should admit that province into the Union as a state. The same policy should be enacted for Greenland.
Canada and the U.S are stronger and more easily defended together as a single polity. No more border patrols. No more passport checks. Alberta can sell its oil from within the US. No more separation of Alaska from the mainland. It’s time.