Let's go back to 1860. Canada is not yet officially a country, but rather a British colony. Since the union of Upper and Lower Canada in 1840 it has been called United Canada.
The province of United Canada had 2 400 000 inhabitants and covered 2,600,000 km 2 , comprising what would later come to be known as the provinces of Quebec and Ontario.
Defending the port of Québec against the Americans was more of an imperial than a colonial issue.