This is such a cliche. I just deleted a long wordy message as to why, but I've lived abroad, speak Spanish, traveled all over and have tons of extended Canadian family, including my maternal grandmother. This sentiment is 100% not true.
I could be in the middle of Tehran or Cairo and tell someone I'm from California and will inevitably get bombarded with friendly questions and stories about how their aunt visited Vermont once, and have I been there. This is the case anywhere I've gone.
I've personally travelled with Canadians. Trust me, no one's eyes light up outside the English speaking world, if that. "Oh, you're from Calgary? Interesting... Is that on the West Coast? Oh, sort of in the middle. Like near Montana?" I mean, it's Canada.
Also, it's not as if anyone wouldn't already know someone is Canadian. They wear red Maple Leaf patches from head to toe, and will even apply fake maple leaf tattoos.
Anyways, it's completely untrue. The US government may not be the most popular all the time, but Americans are treated just fine.