Some people say that in Greece or Italy, the service at restaurants is better for Canadians. If I have a backpack with a Canadian patch, would that help me in some countries?
It depends on what you mean with 'acting like an American' vs. 'acting like a Canadian'.
Americans are (in)famous in Europe for acting as if they own the world, everybody else lives in a third-world country, and everything should work exactly like it works in the USA, because obviously all other processes are inferior.
If you are not doing this, you will be fine, and they will welcome you like any visitor. Just act like a guest; as you would want guests to act when they visit you.