Some thoughts from someone who hasn't done this. Think about the logistics of promotion and marketing. Your book will be available in a country that you may not be able to get to to do school visits, etc. Think about taxes. It's easier for US publishers to work with US authors, especially when the authors have no track record. (Foreign rights sales for a book already out are another matter.) I wonder if the publishers from other countries would wonder whether everyone here had rejected your manuscript already.
(None of this applies for work-for-hire, where the author has sold all rights and often doesn't participate in promotion.)
And, yes, Canadian publishers almost always take only Canadian authors.
I hope the thoughts are helpful. I'm far from an expert on this.