First off, it was three states, not one "becoming global".
The book was not an attack on communism or socialism, it was an attack on totalitarianism. Orwell himself was an ardent socialist at this time in his life, and much of his thematic effort was on revolutions lost to totalitarianism. He wished one in England, and his book is a warning of how his own envisioned revolution could go wrong, as it did in Russia, in fact "Ingsoc" is Newspeak for his own political theory, which he called "English Socialism". The debate amongst his intellectual circle was whether or not England could keep her empire and maintain her relationship with the US as it revolutionized into a socialist state - Orwell was against England maintaining its colonies in this argument, and he saw the US as the ultimate capitalist state and that England needed to leave the US orbit so it could become the leader of a new socialist state formed from post-war Western Europe that would be idealogically opposed to the US. His point in the book is that a corrupting of the ideal, in this case the socialist anti-colonialist ideal, corrupts revolutions - in this case, a socialist England that attempted to maintain an empire would simply mestastisize into a fascist state. There are many, and I am one, who would define Russia under Stalin as a fascist state - a failed socialist revolution corrupted by a Cult of Personality. Germany under Hitler could be seen the same way. The author pulls inspiration from both the Nazi and Soviet regimes. He pictures a world divided between three fascist states who have put the world into a state of endless war, a central tenet of Nazism, for the purpose of keeping their regimes in power. Mr. Bush would fit right in.
Using his own political movement as an example, Orwell shows his vision of how English Socialism becomes Ingsoc as Oceania emerges as a united US/English state that continues to maintain it's empire, in much the same way Russia metasizes into the Soviet red fascist state. As Americans, we have a lot to think about thanks to Mr. Orwell. Under Bush one can see much of what Orwell is trying to say - that good ideas like US democracy can be bastardized and corrupted into something totally different, supported by their bleating sheep fool people all along the way, eventually ending up as some type of totalitarian apparatus that serves The Party -whatever party that might be. My own personal feeling is that American Corporatism is driving the same bus.
Wikipedia has an excellent entry on it:
Nineteen Eighty-Four - Wikipedia, the free encyclopedia