Why Canada might not remain neutral in an Anglo-American war

Would Canada and the other dominions refuse to support Britain in a war connected to Japan?

They might wish to remain outside it, but American plans against Canadian territory and imperial trade could pull Canada into the war and change public attitudes dramatically.

The British Empire's evolution into the Commonwealth was a different process from simple imperial collapse because the new association retained close ties among its members. American contingency plans then complicate Canadian neutrality by calling for attacks on British and imperial trade in the Pacific and an invasion of Canada. Canada might prefer to stay out, but a pre-emptive American move could pull it into the war before Britain made its own choice and sharply change Canadian public opinion. Even superior continental resources would not prevent a wider Anglosphere war from inflicting losses so severe that every major participant suffered. Whether American troops appeared as liberators or aggressors would depend on who widened the conflict and whether Britain had ignored the Statute of Westminster to force Canada into the war.