I'll go with Russia, because they were at least at one point in history, as good, or nearly as good.
Both are decent rivalries, but neither is all that great really. The reason being is that Canada is the clear better team than both the Russians or the Americans historically. How can you consider any rivalry all that good, when one team has basically dominated the entire history of the sport? They are the dominant team, so they can really only be compared to themselves of the past, and their rivals are little in comparison.