I've been thinking about the analogy you make between pluralism in domestic affairs and realism in foreign affairs. There appears to be a confusion here. Isn't pluralism in foreign affairs, after all, the opposite of realism in foreign affairs? Realism says that there is a rational calculation that can be made about what America's national interest "really" is. The realists say that if you look at the correlation of forces in the Middle East, it's folly for us to be supporting Israel, and that lobbying by interested parties on behalf of Israel has distorted our foreign policy and placed it out of alignment with our "actual" interests.
The pluralists say that the American national interest is whatever the American people believe it should be, and because most Americans support Israel, supporting Israel is by definition in the American national interest, and there is no such thing as a rational "realist" calculation that can stand over and above this desire.
Pluralism in domestic affairs also argues that interest group politics is the only politics there is and that invocations of a "public interest" that stands over and above the petty politicking of narrow interests are just ways of disguising a discrete bundle of narrow interests. It's Progressivism that says that we have a transcendent public interest that our best intentioned, most enlightened liberal intellectuals and their political allies can incarnate.
Then again, I can also see how both domestic pluralism and foreign policy realism are analogous in that they both eschew transcendent politics.
It seems to me that the relevant axis here is between democratic and monarchical politics. "Realism" is the watchword of monarchical politics; in domestic politics, it's the king who claims to be the only person able to represent in himself the unified general will of the people as a whole.
There are certain things, like national health insurance that have only one interest group: and that would be "everybody". Narrower interest groups, however -- private insurers, doctors, hospitals, etc. -- have a clearer sense of their own immediate interests, and the ability to mobilize in their defense to block everybody's interest in favor of their own. (They will, of course, argue that their own interest is everybody's interest, as they did back in the 90's, but this won't really be true.)
The mobilization required on behalf of national health insurance would call for someone to incarnate "everybody's" interest. And since no concrete set of pre-existing institutions represent that interest, we need someone to stand over and above the existing set of narrow interests to incarnate everybody's interest. For this, we need a strong unitary center of power -- a strong executive, as the liberal reformers of the Kennedy Administration argued. Enter Obama -- that's the wish he incarnates: the desire for a king. Our multicultural, meritocratic king. It /does/ feel a little bit apocalyptic in its grandeur.
Maybe you would classify what I call "everybody's" interests as something more like "consumer's interests"?