In acting unilaterally last week to allow illegal immigrants who have been living in the United States for more than five years to become legal residents, Barack Obama boosted presidential power, stoked right-wing fury, and likely strengthened Hispanic allegiance to the Democratic Party. He also did something else: He struck a blow for American exceptionalism.

American exceptionalism, you’ll remember, is something Obama’s critics claim he doesn’t believe in. “Our president doesn’t have the same feelings about American exceptionalism that we do,” Mitt Romney said during the 2012 presidential campaign. In a 2010 cover story in National Review, Rich Lowry and Ramesh Ponnuru declared, “At the heart of the debate over Obama’s program is the survival of American exceptionalism.” The more Obama implements his agenda, in other words, the less exceptional America will become.

But on immigration, the truth is exactly the reverse. American exceptionalism has meant different things to different people at different times. In the 19th century, many Americans looked at Europe’s constant war-making and declared their own country to be exceptionally unmilitaristic. But one consistent feature of exceptionalist discourse has been the idea that America permits greater upward mobility than does the Old World. Alexis de Tocqueville wrote, “Among aristocratic nations … families remain for centuries in the same condition,” but in the U.S. “new families are constantly springing up, others are constantly falling away, and all that remain change their condition.” Karl Marx argued that in America, “though classes, indeed, already exist, they have not yet become fixed, but continually change and interchange their elements in a constant state of flux.”

In recent decades, sadly, the reality of American mobility has diverged sharply from the myth. There is today less movement up and down the class ladder in the U.S. than in much of Europe. But in giving millions of undocumented immigrants a path to legalization, Obama is bringing the dream of exceptional American mobility a bit closer.

That’s because the undocumented constitute a separate caste, barred from the rights and obligations enjoyed by other Americans, and thus denied any real hope of rising economically. As Danny Vinik recently noted in The New Republic, undocumented workers often fear that leaving their job, and seeking a new one, will tip off the authorities and get them deported. As a result, they have little leverage over their employers and are easy to mistreat. Vinik cites a 2009 National Employment Law Project study that shows that 26 percent of undocumented immigrants earned below minimum wage. But when the undocumented become legal, they can leave exploitative employers and dead-end jobs for ones that offer greater opportunity. Vinik notes that since 2012, when Obama halted deportations for undocumented immigrants under the age of 30 who had come to the U.S. as children before 2007, almost 60 percent of the newly legalized have found new jobs, and 45 percent have seen a boost in wages.

When Americans invoke the myth of exceptional upward mobility, we often imagine someone who strikes out on her own, transcending the limitations of her current circumstance by starting a business or getting a degree that affords far greater rewards. But ironically, such risk-taking requires security: the security of knowing that switching jobs or careers won’t get you deported. (Knowing that you won’t lose your healthcare helps too.) For millions of Americans, that’s what Obama’s immigration move makes possible.

As Obama himself has acknowledged, his unilateral action isn’t sufficient. While making some of the undocumented legal, it still won’t make them citizens. Until Congress acts, they will still represent a separate caste. But their opportunities for economic mobility—and with it cultural assimilation—have just shot up. Will those opportunities come at the expense of some other Americans, whose legal status had previously given them an economic advantage? Sure. But that’s the whole point of class mobility. When men and women becomes masters of their own fate rather than prisoners of circumstance, some rise and others fall.

America, Marco Rubio said a few years back, “is the only economy in the world where poor people with a better idea and a strong work ethic can compete and succeed against rich people in the marketplace.” That’s not actually true. But it’s truer today than it was last week because the president who supposedly wants to make America more like Europe has instead made America more like its best vision of itself.