He has called Justin Trudeau “very dishonest and weak.” …But on Friday, as President Trump, Mr. Trudeau and Mexico’s president, Enrique Peña Nieto, signed a North American trade pact after 14 months of acrimonious negotiations, the leaders of the United States and Canada appeared cordial… even as their words and body language in recent months have suggested that their once-warm rapport had become as icy as a Canadian winter. In negotiating the United States-Mexico-Canada Agreement, Canada won concessions including a dispute resolution system for companies that feel unfairly targeted with taxes. …In return, Canada agreed to, among other things, Mr. Trump’s repeated demands that it crack open its long-protected dairy market. But the brinkmanship leading up to the agreement was bruising and Mr. Trump’s tariffs on Canadian metals remain in place, severely testing the relationship between Canada and its biggest and most important trading partner.