A survey done in May by the Atlantic and the Aspen Institute found that Americans are feeling bleak about the prospects for U.S. power and influence abroad. Forty-three percent think America’s global standing will be in decline a decade from now (30 percent think it will be rising). While 68 percent think China will be a superpower in 2024, only 44 percent think the U.S. will be; 55 percent think China will be “the world’s biggest economic force” by then (just 20 percent think the U.S. will be).

These figures may not seem concerning when placed in historical context. The public has gone through many cycles of declinism in the postwar era, after all, each of which was followed by a restoration of America’s economy and its leadership abroad.  One could argue, in fact, that a healthy dose of fear has been essential to the country’s regenerative capacity. As Samuel Huntington quipped a quarter century ago, the U.S. “is unlikely to decline so long as its public is periodically convinced that it is about to decline. . . . The more Americans worry about the health of their society, the healthier they are.”

It is not clear, however, that the current cycle of declinism—dating to the onset of the global financial crisis in late 2008—is making Americans “healthier.” According to a report last month by the Pew Research Center, 49 percent think America’s “best years” are over. According to the Atlantic/Aspen Institute survey, moreover, only 35 percent think the U.S. will be headed in the right direction a decade from now. Remarkably, 55 percent think the world will be less peaceful then than it is now, with a fifth predicting U.S-China armed conflict.

Even if the declinist thesis proves to be premature once again, it can undermine U.S. foreign policy if it gains sustained traction among the public. The good news, contrary to much analysis, is that Americans have not become isolationist. According to a Pew report this past December, 66 percent think the U.S. should play a more active role in the global economy, and only 12 percent think it should play no leadership role (72 percent think it should play a shared leadership role). Reflecting the costs over more than a decade of wars in the Middle East, surveys consistently demonstrate that Americans support a diplomacy- and economics-driven foreign policy that sets a high bar for military involvement in crises around the world. This stance is both prudent and sustainable. Should Americans’ current pessimism stick, however, it is not hard to imagine that their proper promotion of selective engagement could morph into advocacy of something closer to retrenchment. Already, according to the Pew report from last month, only 35 percent think “it’s best for the future of the country to be active in world affairs.”

While one hopes Americans will cheer up, there are reasons to expect that their pessimism—about America’s role in the world, at least—will prove more enduring. Two have received considerable attention:

• With public debt, income inequality, and political dysfunction all growing, so, too, are Americans’ concerns about the threats they pose to U.S. leadership abroad.  If a country can barely keep its own house in order, the argument goes, how can it be expected to deal with chaos and complexity beyond its borders?
• The shift of power from states to nonstate actors has accelerated dramatically in the past decade, making international affairs seem even less susceptible to U.S. influence than they were in previous cycles of declinism.

A third reason has received less attention: The rise of China is challenging Americans’ longstanding understanding of power. Policymakers, analysts, and citizens alike often frame it in terms of, or at least associate it with, headline-grabbing metrics such as gross domestic product and defense spending. Neither the Soviet Union nor Japan seriously contested America’s lead in either economic or military terms. Along current trend lines, however, the U.S. will soon cede to China the title of world’s largest economy—a title it has held for at least a century and a quarter. The International Institute for Strategic Studies projects, moreover, that it could cede to China by the mid-2030s the title of world’s largest defense spender—a title it has held since the end of World War II.

These transitions need not be grounds for alarm. GDP is only one component of economic power, just as defense spending is only one component of military power. There are also critical forms of power that cannot easily be quantified: How does one measure, for example, the strategic benefits the U.S. enjoys by virtue of having more than fifty allies and occupying prominent positions in major international institutions? The fuller a conception of power one adopts, the more likely one is to conclude that the U.S. has now, and probably will retain for at least several decades more, an unrivaled pool of resources with which to shape global order.

In a recent essay for Foreign Policy, former U.S. national security advisor Tom Donilon argues that the U.S. possesses at least five “core strengths” that will ensure its preeminence “for generations to come”: “economic resiliency,” “military might and alliances,” “the luck of geography,” “demography and immigration,” and “the virtues of leadership.” The irony is that U.S. observers tend to take a dimmer view of its overall power than China does.

Reflecting on the reception to his new book Still Ours to Lead, Brookings scholar Bruce Jones notes that “China’s managers and scholars are more realistic about the continuing gap between China and the United States than many of America’s home-grown declinists.” If Americans cling to a conception of power that accords outsized importance to the U.S.’s ranking in certain categories, their present pessimism may well devolve into fatalism. Along current trend lines, after all, China will continue to overtake the U.S. in one eye-catching category after another (for example, consumer spending and stock-market capitalization). The United States can and should continue to play an active role in the world; it cannot do so, however, if Americans believe it is in terminal decline and incapable of renewing itself.