An interesting question.
1984 obviously draws on Orwell's experience as a journalist and war broadcaster with totalitarian states - primarily the USSR and secondarily Nazi Germany, I would say - but this is, I would argue, not the primary influence or inspiration for the book. The setting of the book in Britain is not simply an "it could happen here" gimmick or a Red Dawn-style "audiences only care if it's happening to their own country". No.
The primary inspiration for the book in my view is Britain itself during the war, and to a lesser extent afterwards. I argue that the 1940s were a dark time for democracy and liberty in more ways than simply 'there are some nasty totalitarian powers over there invading people': they were being eroded at home. Britain had not held an election since 1935, and the national government meant that all the parties were united, with disagreement being stifled and naysayers like the Independent Labour Party being lambasted as traitors. Ideology was swept aside as irrelevant, but the government possessed control over broadcasting and every facet of public life. Complaining about rationing, for example, would be letting the side down, and propaganda about eating less and eating poorer food being one's patriotic duty was widely circulated. (My grandfather maintained to his death that it actually made him prefer powdered egg to the real thing...)
America, viewed until recently as the chief torchbearer of democracy and liberty throughout the world (regardless of whether those things were viewed as positives or not) was also stuck in a less intense but nonetheless precarious situation. If FDR's health had been better he could have become president-for-life with his personal popularity combined with his electoral machine sewing up victories. The AmeriRight nowadays, shrill though they are, are right to point to FDR's reign as the time when the power of the federal government and the presidential executive unequivocably rendered the states irrelevant. Government power was supreme everywhere for the first time.
My point is that when Orwell conceived 1984, it seemed as though democracy could be on the way out throughout the entire world, and it was this that informed the idea that if every state could degrade to a propaganda-spewing totalitarian dictatorship run by only a minority elite who have any idea of an objective truth, then could those elites establish contact and set into motion an endless war in order to keep their own populations down as powerless serfs? At first so that they would enjoy the best things in life as the ruling class, but eventually just for the sake of power itself.
Now, my point about all this is that it came about due to the length of WW2. If on the other hand Britain had crashed out in 1940 and held elections, any work of this type written by Orwell would have been quite different, probably more like his slant on Invasion Literature. Perhaps a book in which Nazis and Soviets (or their fantasy analogues, like the pigs in Animal Farm) are locked in vicious endless ideological struggle, but emphasising that their differing ideologies are both just excuses to stay in power (Hitler and Stalin or characters representing them knocking back champagne over the dinner table as Stalingrad goes on etc.)