The whole scenario is ridiculous, either Canada would declare strict neutrality to avoid invasion or Britain would never join the Entente because it has no hope of winning a war against both Germany and the USA. If there is a war, 90% of the fighting takes place from the mouth of the St. Lawrence to the Ontario peninsula and Canada has fallen by 1916. But why is Britain wearing the dunce hat in this scenario? How does British policy remain exactly the same when a major peer competitor is about to join the fray? Britain would tell France and Russia in no uncertain terms that she wouldn't get involved if there was a potentially hostile America afoot. This is the same Britain that wouldn't cansider an alliance with Russia until they got thumped by the Japanese. If there's a hostile America it's probably Britain moving closer to the CP to shore up its European commitments.