Political map of North America & the Caribbean 1 July 1867 (Canadian Confederation): US expansionism (Manifest Destiny), its purchase of Alaska (Alaska Purchase) and its alleged support of Irish Republican Fenian raiders (Fenian raids) encouraged the British to listen to demands for self-government and unification from its remaining North American colonies (British North America). In 1867, they assented to the formation of the Dominion of Canada by uniting the British colonies of Canada, New Brunswick and Nova Scotia (Canadian Confederation).