The First russian settlement in North-America was established in 1740s, so they will quite likely be an emerging faction. Russians never succeeded to establish a bigger more stable colony in Americas, but it is always possible to change history. The main reason why they are included is to bring more action to Tlingit and Haida campaigns(more info in preview coming quite soon).
Yes, it's true, many native factions never had a change to challenge the whites, but some stronger tribes, such as Apaches, Tlingits and the Iroquois Confederacy did have enough ppower to do so. Not sure about the Canada thing, as we are not going to include 19th century(maybe later), but it would be possible to extend the campaign to 1810s-1820s to get the 1812-1815 War and Tecumseh in.