Couple of things: As a Canadian, even if a full time lawful U.S. resident, you cannot _document_ the boat as US. You can purchase it, get title, even get state stickers to legally have the boat reside and sail in a state, but not documentation.
Even if the boat never travels to Canada, you can do Canadian documentation (which, confusingly from an American perspective, is called registering):
Procedures for Registration in Canada - Transport Canada
The two exercises are distinct. Legally owning and operating a boat in a given jurisdiction (mostly about paying taxes and fees) versus documenting/registering (mostly about certain legal rights in international waters and other countries).