How about this:
Because the Anarchists seized sizable sections of the USA, America recalled all her troops from the middle east at short notice, this forced the UK to increase the numbers of troops committed in order to maintain stabilty in the region, this left the UK with virtually no military based at home. Inspired by the success of their American counter parts, British Anarchists struck, and with almost all the UK's troops deployed abroad quickly took control of all the UK's major cities, wich the exception of Glasgow, which fell to Scottish Nationalists. Very quickly Anarchists accross Europe followed the American and British example. As most European nations still had troops at home they were not as successful as their British counterparts, Paris, Berlin, Krakow, and Barcelona fell quickly, and after some resistance other parts of the EU followed suit.
This is where the game begins: The EU is fighting the Anarchists, but will the member states stay united, or, will some use the chaos as an opportunity to turn on their allies and begin working to unite Europe under their own Imperialistic mode? The British Government is operating in exile form Gibralter and is desperate to regain control of the UK, they have a small guard in Gibralter, and loyalist paramilitaries in the countryside around London, and Edinburgh, Belfast is still nominally under British control but surrounded by hostile anarchists. Manchester, Liverpool, Birmingham, and Leeds are firmly under Anarchist control. Each EU Member will be a different Civ, but allied with each other, as the game plays out they may remain allies or turn on each other; maybe Spain will use this opportunity to seize Gibralter, thus leaving Britain with only Belfast and that looking likely to fall soon. To the East Russia, The Ukraine, and Turkey are all remaining neutral for the time being, but how long will that last? If Russia decide to regain their old sphere's of influence, will the Communists try to regain power, using the war, as they did during WWI as an opportunity? Maybe Britain will be able to recall their military, giving them a sudden surge of battle hardened veterans part way through the game (allowing a future spin of mod since at that point the Middle east would descend into chaos). Maybe late in the game, America will have fallen fully to the rebels, who then send support to their European comrades.
There would have to be a lot of Civs in this, more than the 18 in a standard game, the EU alone has 22 memeber states, I would suggest the following as a minimum which may make it unworkable:
European Rebel Alliance (some cities in all civs that are marked with a *)
The EU (All allied with each other at the start but with friction that may break up the alliance):
Austria*
Belgium*
Bulgaria
Cyprus
Czech Republic*
Denmark*
Estonia
Finland*
France*
Germany*
Greece*
Hungary
Ireland
Italy
Latvia (large ethnic Russian population)
Lithuania
Luxembourg
Malta
Netherlands*
Poland*
Portugal*
Romania
Slovakia
Slovenia
Spain*
Sweden*
United Kingdom*
Russia (cautious to all other nations, except possibly the Ukraine and Belorus)
Turkey (very friendly to the EU, however eastern EU nations are hostile to Turkey)
Norway* (friendly to all EU nations, especially Sweden, Denmark, and Finland)
Croatia (hostile to Serbia, very friendly to EU nations)
Serbia (hostile to Croatia)
Bosnia
Maccedonia
Switzerland (friendly to the EU - very strong defence force - rich)
Ukraine
Belorus
Iceland (neutral, unlikely to get involved unless invaded)
Scotland (only have control of Glasgow)
That makes at least 40 Civs, is that possible? The game would start similar to the American version, but the overiding theme would be history repeating as old buried rivalries rear their head. There are lost of possibilities, both Paris and Berlin have fallen, will Germany and France work together to regain order or will they turn on each other? Will Ireland attempt to seize Belfast? Can the Scotts take Edinburgh, will the UK ally with the Scotish or see all insurgents equally as they try to take back the mainland?