Climate change warning: Greenland once melted and raised the ocean 5 feet.

F or years, Canadians have operated on two competing assumptions: that Americans like them and that Americans barely think of them at all. New polling from Leger suggests both instincts are correct, even amid continued trade tensions between Ottawa and Washington. In a survey of 1,004 American voters conducted April 17–20, Canada remains one of the few nations Americans still view with overwhelming warmth. Asked how they would describe Canada in the context of the economic and trade relationship, a majority characterize the country in broadly positive terms. But the data is shaded with...