Trump wants to annex Canada! You can’t say it hasn’t been tried before. There was an unsuccessful American invasion of Canada in the early days of the Revolutionary War, and annexation was one of the two principal reasons (impressment obviously being the other) behind the American declaration of war in 1812.
But there have been no serious disputes between America and Canada since the 19th century, which has been a great diplomatic success for both parties. With some bad luck and worse policy, Canada could have become America’s version of Ukraine. Who would want that?
Putin and Xi, for starters.