Really. Do you get called Yank a lot? I have never heard the term used here (in Québec).
As to the Canadian couple...it was probably just a protective reaction. Please please please do not take this as an attack, just as a bit of info. Canadians get treated much better when they say they are Canadians than when they let people believe they are Americans.
Unfortunately, there are still biases in this world. One of them is the belief that ALL Canadians are these self reserved individuals, sorta dull but all-around honest good people. Americans are often viewed as loud and self-serving. I have known several friends who were treated badly because people thought they were Americans (in France 2 and Italy 1) and the situation changed markedly when they let people know they were Canadian. I also have a friend from New Jersey who says he is from Canada when he travels overseas. He has noticed the same bias.
This is such a common situation that we are often told to wear Canadian pins or badges when we travel overseas and to let people know right away that we are Canadian.
I believe judging a person without knowing him is unjust, but not everybody does.
