Head Movements
Canada and the U.S. might share a border, but sometimes it seems like it could be another part of the world altogether. Everything from their social norms to their language is different. They even have different head gestures! In Canada, when you bow your head down to a stranger you show respect, and the opposite, if you bow your head up to a stranger you are challenging them.
But it gets more complicated: this logic only applies to strangers. When it’s a friend or a close person, you bow your chin down to indicate agreement, and nodding your chin up towards a friend is a greeting. This might not be a cultural thing in Canada, though, but specific to the city where this person lives. I guess you won’t know until you visit Canada.