First off, I like the idea of an MMOFPS. Would be totally awesome.
However, your MMO is TOO Cliche. It's really big, and the easiest thing would be to shrink it. How, you may ask?
Western Europe-2182
Devastated by multiple terrorist bombings, seperatist revolts, and water riots, the EU collapses. Requesting help from other nations, they quickly move in to assist the beleaguered continent. Russia, allied with Ukraine and the eastern nations, moves in around Poland, rebuilding. The Balkan nations, along with Greece, Turkey, and the North African nations, move into Italy. The US and Canada naturally moves in to help their long-standing ally, the UK, using Ireland as it's base of operations. The south american countries move in a reversal of colonialism, taking over the Iberian peninsula. China, realizing the time being ripe for conquest, utilizes mobile airbases and takes Hungary. The other nations don't take much notice, as the damage is horrendous.
Western Europe-2202
It has been 20 years since the Tragedy occured, yet the assisting nations have yet to leave their areas. Europe, united under a new banner of neo-national socialism, hold the most territories, including the Benelux, France, Germany, and the Bohemian region. Tired of the occupation their territory has suffered, it has declared war on all nations not willing to withdraw. However, previous alliances somehow force everyone to declare war on everyone else, except for China. China, with it's annexed property of Hungary, is somehow immune to all the warfare. Considering the fact that the Dragon is one of the most aggressive nations, this perplexes most political and military strategists.
Furthermore, the Middle East has banded together under an organization known as INCHALLAH (Literally "God willing"), and rally a powerful Jihad that all Arabs must heed.
The stage is set. This is now WAR!
And there's your backstory, minimized region, and still-cliched nations.