BBC America has stated that the trip to Canada will be a "state visit"and Hello Magazine declares that whilst in Canada the royal newlyweds will be "flying the flag for Britain", with Prince William's wife acting as a British "ambasadress".
Let's get the protocol straight:
During their Canadian tour The Duke and Duchess of Cambridge will be flying the flag for Canada not Britain. Prince William and his wife will be the future King and Queen of Canada. When a member of the Royal Family visits Canada, Australia, New Zealand or any of Her Majesty's 15 realms outside the UK, they are not acting as "Ambassadors" for Britain, they are representing the Canadian Crown, Australian Crown etc. This is an important distinction.
The Duke and Duchess of Cambridge were invited by the Canadian government and the trip will be paid for by Canadian taxpayers. Britain and the British government play no role whatsoever in the relationship between Canada, the Canadian government and the future King of Canada.
Similarly, The Queen and members of the Royal Family do not make "state visits" to Commonwealth Realms. Such trips may be styled "Royal Tours", "Royal Visits" or even "Royal Homecomings" but certainly not state visits.