Every Canadian student of foreign policy knows the story, but few Americans remember. In 1965, at the height of the Vietnam War buildup, Prime Minister Lester B. Pearson suggested to a college audience in Philadelphia that the United States stop bombing North Vietnam in the pursuit of a negotiated settlement. President Lyndon B. Johnson was not amused. When the courtly Canadian leader stopped by for a visit to Camp David, Mr. Johnson grabbed him by the lapels and accused him, in so many words, of soiling his rug. Emotions are a bit lower now, and President Bush is likely to...