Here’s what Daniel Larison says at THE AMERICAN CONSERVATIVE. He’s not completely wrong:
The claim about American’s capacity to project power is an empirical one, and it is informed by the experience of the last decade. Many, if not all, realists acknowledge that the U.S. is in relative decline, but they do not necessarily claim that the U.S. is doomed to suffer absolute decline. The first may be unavoidable, but the second does not have to be. Many of the recommendations that realist advocates of a foreign policy of restraint and prudence make are designed to husband American resources and power rather than frittering them away in a fruitless maintenance of hegemony.
Realists do not dismiss the role of ideology and beliefs in motivating political actors, but they do often object to allowing them to direct the making of foreign policy because of their potential to blind policymakers to inconvenient realities and potential risks. Realists also tend not to put much stock in ideological justifications for policies, because these justifications are most likely providing rhetorical and political cover for other reasons. They are also usually wary of justifying policies in ideological terms, because this makes it much more difficult to cut one’s losses in a war, reach necessary negotiated settlements with unsavory groups and regimes, or cooperate with regimes that do not share our political assumptions and values. A national missionary impulse can also lead the government to engage in conduct abroad that contradicts core American values on the grounds that the ends justify the means. If realists generally eschew the rhetoric and assumptions of a missionary foreign policy, they do so more because they regard the policies needed to carry it out to be too costly, too open-ended, and too disconnected from the security and well-being of the United States.
Realists may or may not subscribe to a view that America is exceptional in terms of its political institutions and values. I assume that most, if not all, realists do think that America is exceptional in this way. Indeed, if this all that the new enthusiasts of American exceptionalism meant by the phrase, no one would be arguing with them. What realists do tend to find obnoxious is the presumption and arrogance embedded in the hegemonist version of American exceptionalism. This version requires its adherents to identify American exceptionalism in terms of economic and military superiority and to make a point of disparaging other nations by comparison. What hegemonists mean by American exceptionalism is simply a form of hard-line nationalism and enthusiasm for global hegemony.
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