Canada is a Commonwealth country. We speak English AND French at all levels and provinces (though not so much French in BC, and not so much English in Quebec), but both languages are official languages. When I became a citizen, I pledged allegiance to the Queen and her heirs and assigns, as she is our Queen as well. (Even in Quebec.) We have a Governor-General who is the Queen's representative in Canada. S/he is appointed by the Queen on the advice of the (Canadian) Prime Minister. Tenure is “at pleasure” and usually lasts five years, but this term may be extended.
OTOH, the UK has absolutely nothing to do with our legal process any more beyond the G-G signing all laws as the Queen's representative and reading the 'throne speech' in the Canadian Parliament to open the session. (Canadian equivalent to State of the Union in the US.)
My ability to buy books from Amazon/AudibleUK has absolutely nothing to do with my living in Canada. But everything to do with my having a UK Amazon account and a UK registered Paperwhite.
My primary Amazon and Audible accounts for eBooks and audio books are both US Amazon accounts. I also have a separate Amazon.ca account I use for eBooks that I can't easily get from Amazon US. (Not many, but a few.)