“”” Charles III, by the Grace of God, King of the United Kingdom of Great Britain and Northern Ireland and of His other Realms and Territories, Head of the Commonwealth, Defender of the Faith. “””
So in my head canon, he is the King of the UK and Canada … the same person and the same office. Ie there is no King of Canada officially - the title is always King of UK (first) and of other places as well … in short whilst Canada has a King, there is not a title “King Of Canada” that he can hold as well as holding “king of UK”