Iran's General Mohammad Bagheri calls for increased security cooperation between the two countries.

Americans voted for change in this week’s presidential election, and in foreign policy, they’ll certainly get it. Donald Trump has shown disdain for the priorities and precedents that have traditionally guided Washington’s approach to the world. He speaks more fondly of America’s autocratic adversaries than of its democratic allies. He derides “globalism” as a liberal conspiracy against the American people. And he treats international agreements as little more than wastepaper.

At stake is not only the survival of Ukraine and the fate of Gaza, but the entire international system that forms the foundation of American global power. That system is built upon American military might, but more than that, it is rooted in relationships and ideals—nations with shared values coming together under U.S. leadership to deter authoritarian aggression and uphold democracy. The resulting world order may be badly flawed and prone to error, but it has also generally preserved global stability since the end of World War II.

Despite its endurance, this system is fragile. It is sustained by an American promise to hold firm to its commitments and ensure collective defense. Trump threatens that promise. His plan to impose high tariffs on all imports could disrupt the liberal economic order on which many American factories and farmers (and Trump’s billionaire buddies) rely. His apparent willingness to sacrifice Ukraine to Russian President Vladimir Putin in some misguided pursuit of peace will strain the Atlantic alliance and undermine security in Europe. By signaling that he won’t defend Taiwan from a Chinese invasion, he could undercut confidence in the United States throughout Asia and make a regional war more likely.

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The American global order could end. This would not be a matter of “American decline.” The U.S. economy will likely remain the world’s largest and most important for the foreseeable future. But if Washington breaks its promises, or even if its allies and enemies believe it has or will—or if it fails to uphold democracy and rule of law at home—the pillars of the American international system will collapse, and the United States will suffer an immeasurable loss of global influence and prestige.

The risk that this will happen has been gathering for some time. George W. Bush’s unilateralist War on Terror strained the international system. So did Trump’s disputes with NATO and other close allies during his first term. But world leaders could write off Washington’s wavering as temporary deviations from what has been a relatively consistent approach to foreign policy over decades. They understand the changeability of American politics. In four years, there will be another election and a new administration may restore Washington’s usual priorities.

With Trump’s reelection, however, the aberration has become the new normal. The American people have told the world that they no longer wish to support an American-led world order. They have chosen U.S. policy makers who promise to focus on the home front instead of on the troubles of ungrateful allies. Maybe they’ve concluded that the United States has expended too many lives and too much money on fruitless foreign adventures, such as those in Vietnam and Afghanistan. And maybe now America will reassess its priorities in light of new threats, most of all China, and the potential burden of meeting them.

The problem is that if the United States won’t lead the world, some other country will, and a number are already applying for the job. One is Putin’s Russia. Another is the China of Xi Jinping.

China began to assert its global leadership more aggressively during Trump’s first term and has worked ever harder to undermine the American system since—strengthening China’s ties with Russia and other authoritarian states, building a coalition to counterbalance the West, and promoting illiberal principles for a reformed world order. Trump seems to believe that he can keep China in check with his personal charm alone. When asked in a recent interview whether he would intervene militarily if Xi blockaded Taiwan, he responded, “I wouldn’t have to, because he respects me.”

That’s narcissism, not deterrence. More likely, Putin and Xi will take advantage of Trump’s disinterest. Once appeased in Ukraine, Putin may very well rebuild his army with the help of China, North Korea, and Iran, and then move on to his next victim—say, Georgia or Poland. Xi could be emboldened to invade Taiwan, or at least spark a crisis over the island to extract concessions from a U.S. president who has already suggested that he won’t fight.

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The result will be not merely a multipolar world. That’s inevitable, whatever Washington does. It will be a global order in which autocrats prey on smaller states that can no longer count on the support of the world’s superpower, regional rivalries erupt into conflict, economic nationalism subverts global trade, and new nuclear threats emerge. This world will not be safe for American democracy or prosperity.

The fate of the world order and U.S. global power may seem of little consequence to Americans struggling to pay their bills. But a world hostile to U.S. interests will constrain American companies, roil international energy markets, and endanger jobs and economic growth. Americans could confront bigger wars that require greater sacrifices (as in 1941).

Perhaps Trump will surprise everyone by pondering his legacy and choosing not to pursue the course he has signaled. But that seems unlikely. His messaging on his foreign-policy priorities has been too consistent for too long. Over the next four years, Americans will have to decide whether they still want the United States to be a great power, and if so, what kind of great power they wish it to be. Americans wanted change. The world may pay the price.