There will be some small European nations surviving; those in Eastern Europe still largely dependant on the Rus and GH.
The ideas I have for surviving nations are a Gaelic-Scot nation in the Highlands of Scotland, perhaps a English-Scandic city state centred around Lindisfarne (you'll understand why when I post my history of Europe
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), the mighty city state of Flanders, the Papacy in Barcelona, Granada in Granada, a spanish nation based in Asturias, a Catalan nation based in the Baelaerics, the Republic of Corsica (the remnants of the Genoan Republic), the Duchy of Apulia (the remanants of the Kingdom of Naples), perhaps Venice still survives, the Helvetic Confederacy, Viking Hannover/Oldenburg, Germanic Hansa centered around Lubeck, a small Kingdom of Krakov and a small Duchy of Masovia, the Republic of Prague, the Baltic Alliance, Lithuania, the Kingdom of the Rus, The Golden Horde, Transylvania, the Greek city states of Athens, Sparta, the Knights of St John in Rhodes, some Turkish city states in southern Anatolia, the Kingdom of Cicilia ruling Cyprus and parts of Lower Armenia, i also though of having Georgia divided up into Abghazia, Imertia, and Khaheti, and also an independent Derbent and Upper Armenia.
It will of course be possible to play these states just like its possible to play the Native states in Vanilla.
However if and when the Americans arrive then expect to be owned at least until the colonial empires begin falling apart. lol.
Feel free to make any further suggestions.