There is nothing quite so parochial in Canadian foreign-policy debates as the recurring imbecility that the weight of this country’s heavy economic reliance on the United States should be lifted by securing advantages in deeper trade relationships with China. Lately, the proposition can even be made to appear sensible, now that the growing costs of doing business with Donald Trump’s America can’t be properly calculated from one day to the next. So there’s a lot of it going around nowadays.