We grappled with this for the first edition and it comes down to two factors, as far as I can tell.
1) Artistic license.
Artisitic license can be broken down further into in game simulations and then how you want to tell a story. The more disconnected the real world is from the game world, the more freedom you have to explore all sorts of possibilities.
Relevance is the connection with the theme of the game and the stories told to what is actually happening in the real world. My problem is that I'd like the fiction to stand alone as pieces of literature that have something to say about our current geopolitics and such. It is harder to do that when your future history is different from real world events.
But funny you should mention it. About a year ago I toyed with the idea of an alternate history. I tentatively called it LOS: EMPIRE. America lost it's war of independence, Islam swept Africa and south Asia and the Chinese took the rest of Asia. Russia, Europe and South America are sidelined as bit players. WWI happened but I wasn't sure if WWII could be avoided. At the point of open contact (the Fantasians had been in touch with the Germans and Russians for some time) there are only three power blocks: The British Empire, The Chinese Hegemony and the Caliphate. It makes the game simpler than having 200 nations channeled through the UNE only to be a lone voice in the League of Aliens.
But getting back to Relevance, comic books and movies do the retcon all the time to keep the stories relevant.
Sgt. Patterson was UDR and later SAS posted back to Ulster in a counter-terrorist team. He tried to muster out after a 15 year old girl in the IRA tried to kill him and he hesitated (his 2IC killed her first). Command had him transfered to the "Supp List" or supplementary reserve where he existed as a name on a list with a bunch of qualifications that could be reinstated if he so chose. On his departure, he said to his commanding officer, "I can't imagine anything that would bring me back." He said that just as the Legions of Steel were capturing planets on the outer fringe of the galaxy. He returned to England and a loving but dysfunctional marriage and took a "normal" job that he hated. After word of the LOA landing and that soldiers would be needed to fight a mechanical foe off-world, he reactivated himself. The UNE was formed grudgingly, with the major powers recognizing the practical need to be part of the LOA but resenting the institution of a "world government". The dozen or so major powers wanted to field national armies but the smaller, more numerous countries insisted on a dedicated UNE force with the proviso that no UNE force could be operational on Earth itself. A young lieutenant's idealism lead to the Sahara Incident. Meanwhile, national governments offered up their most dysfunctional soldiers to volunteer for UNE service. Patterson was flagged as a problem child because he froze up. Of course, in fighting a mechanical foe, none of these moral quandries arise and he ended up becoming a legend, but went MIA following Junction Point.
So, how do we update this? He served in Iraq? Afghanistan? Got freaked out by a teenage suicide bomber?
Of course, none of this has actually been published, but I would like to in a coherent manner.