Mitt Romney’s stump speech during the Republican primaries was filled with appeals to his party’s conservative base, but none consistently inspired more heartfelt cheers than his promise to “stop the days of apologizing for success at home and ­never again apologize for America abroad.” The statement speaks to the widely held suspicion on the right that liberals in general, and Barack Obama in particular, prefer other forms of democracy ­(especially those that prevail in Europe) to the American way of life.

Martha C. Nussbaum’s new book could serve as Exhibit A in liberalism’s defense against this charge. The author of 17 previous books on a wide range of topics — from classical Greek philosophy and tragic drama to modern law, literature and ethics — Nussbaum is one of America’s leading liberal thinkers. In “The New Religious Intolerance,” she turns her attention to the rise of antireligious — and specifically anti-Muslim — zealotry since the terrorist attacks of Sept. 11, 2001. Though she writes in her opening chapter that intolerance disfigures “all Western societies,” it quickly becomes clear that there have been far fewer incidents of bigotry in the United States than in Europe — because of America’s vastly superior approach to guaranteeing the rights of religious minorities. When it comes to freedom to worship, at least, Nussbaum is an unabashed proponent of American exceptionalism.

Not that she would want to put it that way. Convinced that evenhandedness is both a moral and an intellectual virtue, Nussbaum begins by citing anti-Muslim incidents on both sides of the Atlantic. In the United States, there have been efforts to proscribe the use of Sharia law in wills, marriages and other civil contracts, as well as the dozens of examples of mosques facing vandalism or public protest. In Europe, meanwhile, France and Belgium passed laws prohibiting Muslim women from wearing the burqa in public at the same time that 57 percent of voters in a Swiss referendum supported a ban on building minarets outside mosques. Then there is the Norwegian fanatic Anders Behring Breivik, who said he was motivated to kill 77 people in two attacks in July 2011 out of a desire to fight the supposed Islamization of Europe.

As Nussbaum notes, the American and European developments differ in important ways. Above all, she writes, nothing in the United States “even remotely approaches the nationwide and regional bans on Islamic dress in Europe, or the nationwide Swiss minaret referendum” — let alone an anti-Islamic massacre. In Nussbaum’s view, the difference in severity stems from divergent views of national identity. Whereas European nations tend to “conceive of nationhood and national belonging in ethno-religious and cultural-linguistic terms,” the United States associates citizenship with the affirmation of an ideal of freedom that explicitly precludes the persecution of religious minorities. She suggests that Europe migrate to “a more inclusive and political definition of national belonging, in which land, ethnicity and religion would be less important than shared political ideals.” In other words, Europe should become more like America.