I personally think that it would be set in the FBU, given that Alan Moore is both living there, and because I think that his work would largely be centred on critiquing FBU society and politics from a Communist pro-Comintern perspective.
The general idea I have for the story is that relations between the USAR and USSR break down catastrophically, and as a result a nuclear war breaks out between the various members of the Comintern. After the dust settles the FBU is left the undisputed superpower of an apocalyptic world, and ends up descending into fascism and hyper-imperialism, under the pretext of maintaining order during the ensuing ecological catastrophe, whilst blaming Communism for the devastation of the world.
The political aims of the story would be to critique the inherent authoritarianism and institutional racism within the FBU, and extrapolate it to it ultimate logical conclusion, as well as serving as a counterpoint to those who would justify, or at least explain away, the existing authoritarian elements of the FBU as necessary to combat the threat of Communism, arguing that without a strong socialist/communist movement there would be nothing to prevent the FBU from descending into outright fascism and the worst excesses of imperialism.
That's what I was thinking of. A reducto ad absurdum critique of the authoritarian state. I presume V is going to be more of an American-influenced anarchist.