I did not say that Canada was not in the war, I said how they entered. A few of the countries in the empire like Canada and Australia choose to go to war and declare war separately the where not required to or ordered by the British home office. They did so because the believed they where British and all Brits needed to defend the empire and motherland, during the war that changed.
When the league of nation was formed they where allowed to join as independent nations.
Self governing
Canada -1867
Australia - 1901