I had to look this one up. Yes, I was unaware that "loon" was associated with Canada, via, it appears, various species of waterfowl. Though here in the UK, the same birds are referred to as "divers". Apparently, one species thereof also features on Canadian coinage, and the coin is known as the "loon" for that reason.

One learns something new every day.

However, it also appears that some parts of the USA have cultural attachments to the waterfowl in question as well.

Out of the five known species, the Black Throated Diver (as we call it here) is absent from North America, but the Red-Throated Diver occurs right across the northern hemisphere. Canadian populations thereof are joined by the other three species, of which the Pacific Loon used to be classified as being in the same species as the Black-Throated Diver until 1985. Now it's been determined to be a separate species in its own right. It's joined by the Common Loon (which superficially resembles a larger version of Black-Throated Diver), and the Yellow-Billed Loon. Canada appears to be a popular breeding location for the North American species.

Quite how the word "loon" came to be applied to these birds remains a mystery to me, but I have found that they're amongst the most phylogenetically ancient of modern birds, with a virtually unbroken ancestry stretching back all the way to the Lower Cretaceous.

Here in the UK, the word "loon" is reserved for wingnuts of assorted types, deriving originally from "lunatic", which entered the lexicon when various species of madness were thought to be influenced by the phases of the Moon.