A Special Relationship in Danger

Individuals have friends; nations have special relationships. The term is as close as the cool and stilted vocabulary of political science comes to sentimentality. It refers to a handful of international ties that depend on some combination of cultural kinship, geopolitical advantage, mutual defense and, above all, shared values and ideals.

Americans can take pride in their nation's friendships. Britain is not just a former colonial motherland but also the home of a certain strain of civility that Americans admire. Canada is more than just a giant neighbor; it is also a good neighbor, and its hardiness appeals to America's nostalgia...