Arionhunter of Livejournal offers an interesting thematic theory of the Selected Works of Frank Miller:
Martha Washington is in an interesting place as Miller’s first/only explicit political satire. The satire itself reads as dated, decrying Reagan, the growth of corporations that suppress creativity, nationalized health care, and has an uncomfortable relationship with environmentalism. The government itself is either oppressive or incompetent. Yet everyone who challenges the government is a parody of a cause. The Calvinists, militant feminists, the “gay white racists Nazis.” All of these groups have forgotten “the ideas of America,” themselves embodied by the Captain America figure.
Now, there’s really no way to continue without addressing what seems to be Miller’s evolving politics. What Miller is proposing a kind of ethical moralistic Nationalism. Miller is an authoritarian whose authority comes from one’s strongly held morals, which should always align with those of one’s nation. When the nation deviates from what you hold as the nation’s morals, then you must hold to your morals first. This follows into Miller’s hero, who almost always fights some form of decadent deviance.
I say this because DKR/DKSA leaves no other option. Superman is the figure blindly following the nation in DKR, and in DKSA he is trying to negotiate. At the end he becomes an embodiment of the Nietzscheian idea, using his moral authority to become part of the oligarchy. And I think that’s evident of the evolution aspect. Martha Washington has no “gods and heroes” oligarchy. The God is the nation’s ideals. This is bolstered by the “Captain America” figure; this is the only time you see such a figure pre-9/11. However, by DKSA we (collectively) gone so far that we must have Gods (IE Superheroes). And over time, stronger and stronger “moral” authority figures are required by Miller. 300 is Miller’s love letter to his ideal society, where everyone is willing to give themselves over to the state.
Much more at the link about those three series.