...I like Rawls, too. The man was a giant of 20th c political philosophy, but his impact in the real world has been negligible. Even in the judicial realm, the guy who wrote the book on Justice has had virtually no influence on American jurisprudence. (Does this contradict my previous paragraph? No.) But it didn't need to be so. Rawls was more interested in solving puzzles against Nozick than to be influential in the world at large. That's a pity but that was his choice. On the other hand, Foucault (a deeply original thinker, despite the caricature and some of the idiotic pronouncements he made about Iran) can be credited as much as anyone for the end of capital punishment in France. Not bad for a philosopher who died of AIDS when he was only 57. In this country, if the death penalty is ever abolished, the credit will go to Sister Helen Prejean, a Catholic nun.This is an endlessly interesting question... for philosophers, at least (to the extent that remains so, the answer may be implicit in the question). Rawls defined Anglo-American political philosophy from 1971 on (the year of publication of A Theory of Justice) - everything was a defense of or critical response to Rawls. The discussion with Nozick (particularly the libertarian work of Nozick's Anarchy, State, and Utopia) was but one piece of the broader evolving framework of political philosophy. Communitarianism as a political philosophy and ethics, for example, largely arose as a critical response to Rawls.
It's true that it's difficult to gauge the influence of Rawls in the larger society, but I don't think this influence can be discounted so easily. I've seen Rawlsian arguments appear in the statements of political figures in the US. I've talked with people at the World Bank who learned from Rawls and had integrated some ideas into their work. I've talked with lawyers who have an easy facility with Rawlsian thought. And I've seen Rawlsian ideas worm their way through public policy discussions.
These are all elites in American society, however. Rawls does not appear to have much purchase at all in the broader society, nor among political activists. Most of my grad students have never heard of Rawls before my class where I teach him.
Part of the issue here is that the US is not France. Integral to French culture is its intellectual life. Even if one hasn't actually read Foucault, one knows his name as a giant of French intellectual life. This is obviously also the case with the likes of Jean-Paul Sartre and Simone de Beauvoir, but even with those with whom many philosophers in the US are not familiar (e.g., Michel Serres, Alain Finkielkraut, and philosophers of lesser fame).
US culture is famous for its anti-intellectual streak. This streak maintains that there is the world of ideas and there is "reality." It suspects that too much delving into ideas merely takes one away from reality. "Reality" is thereby often divested of interesting ideas and new frameworks of thought. Or, rather, certain fields that more directly yield a "product" gain pride of place and influence in American intellectual life. Economics, for example, has its philosophical depths but also provides tools for generating tangible income.
Political philosophical ideas have huge influence over the long term. Democracy as a reflective form of political organization was an ancient Greek invention. Our basic ideas of rights were received from the Enlightenment. Maybe it's best that political philosophers content themselves with the long view.
But, honestly, I think this means ceding intellectual territory and practical influence that political philosophy does not need to cede. Rather, it needs to reinvent itself, or parts of itself. On this point, I'd have to agree with Peter Levine (writing in a somewhat different context):
...It's not enough to know whether a given program causes a particular outcome (such as higher incomes, or more civic duty). We must also decide whether those outcomes are good, whether they are distributed fairly, whether any harms to others are worthwhile, and what means for deriving these consequences are acceptable. Further, it's not enough to understand how to run or structure a good program. We must also decide what forms of governance or administration are ethical. (Mussolini made the trains run on time, but that was not an adequate defense of fascism). Finally, it's not enough to know that a given argument or "message" would produce political support for a program. We must also decide which forms of argument are ethically acceptable.
Thus it's a shame that philosophers tend to cede the "middleground" to social scientists, administrators, and tacticians. As a result, no one raises the serious, complex moral issues that arise when one thinks about political tactics, the design of programs, and their administration. This is not only bad for policy and public discourse; it is also bad for philosophy. Theories are impoverished when they miss the middleground...
Some areas of philosophy have developed a middleground and thereby not only served public purposes but also enriched the discipline. Medical ethics is the best example. It's no longer restricted to matters of individual ethics (e.g., should a physician conduct an abortion?) or matters of basic structure (e.g., is there a right to life?), but also to matters of administration, politics, and program design. Medical ethicists work in hospitals, advise commissions, and review policies... I would generalize and say that across the whole range of policy and social questions, it is worth asking moral questions not only about basic rights and individual behavior, but also about institutional arrangements and political tactics.