Whether or not the world is in an unusually bad state these days, it certainly seems so. Even Americans, famous for our lack of interest in world affairs, now closely follow news from far away. Much of it is frightening.

Terror attacks are claiming innocent lives around the world. Syria is being torn apart. China and Russia boldly pursue their national interests and defy American dictates. Turkish democracy is evaporating. Iran and Saudi Arabia are at each other’s throats. Wars in Iraq and Afghanistan drag on interminably. The European Union is staggering, with Britain quitting and others perhaps to follow. Meanwhile, several European countries are drifting toward right-wing authoritarianism. Donald Trump’s campaign threatens to take the United States in the same direction.

This is the opposite of what many Americans expected. The collapse of the Soviet Union in 1991 set off a wave of triumphalism in the West. Americans welcomed the “end of history’’ and presumed that all countries would quickly adopt political and economic systems like ours. There was to be a “peace dividend’’ as tranquility settled over the globe. People would become more prosperous. Nations would cooperate. All would gratefully submit to America’s will.

Those were delusions. The world has gone in precisely the opposite direction, toward tribalism and conflict. We are now paying the price for grave misjudgments.

The first was our misunderstanding of the Soviet collapse. It was a Soviet failure, but we interpreted it as an epochal American victory. That led us to believe that in a post-Cold War world, American power would grow, turning us into a global hegemon that other countries would happily follow. This was never realistic.

Moments of change require adaptation, but the United States is not good at adapting. We are used to being in charge. This blinded us to the reality that as other countries began rising, our relative power would inevitably decline. Rather than shifting to a less assertive and more cooperative foreign policy, we continued to insist that America must reign supreme. When we declared that we would not tolerate the emergence of another “peer power,’’ we expected that other countries would blithely obey. Instead they ignore us. We interpret this as defiance and seek to punish the offenders. That has greatly intensified tensions between the United States and the countries we are told to consider our chief adversaries, Russia and China.

The ideological conflict of the Cold War was so intense that when it ended, Americans assumed tranquility would follow. In fact, the Cold War was simply a temporary phenomenon that masked centuries-old political, social, cultural, and religious conflicts. Nationalism and tribalism, which began shaping the world long before Communism was invented, have reemerged rather than fading away.

Our wrongheaded reaction to the end of the Cold War was America’s first major contribution to today’s global turmoil. The next was our decision to invade Iraq. That invasion continues to shape the world. The recent surge in Islamist terror is one of its long-term results. So are the refugee flows that have destabilized Europe and contributed to the rise of extremist political movements there. It is an object lesson in the long-term effects of intervening in faraway lands — a lesson we still seem not to have learned.

Because we interpreted the end of the Cold War as the ultimate vindication of America’s economic system, we intensified our push toward the next level of capitalism, called globalization. It was presented as a project that would benefit everyone. Instead it has turned out to be a nightmare for many working people. Thanks to “disruption’’ and the “global supply chain,’’ many American workers who could once support families with secure, decent-paying jobs must now hope they can be hired as greeters at Walmart. Meanwhile, a handful of super-rich financiers manipulate our political system to cement their hold on the nation’s wealth.

Our leaders told us that the end of the Cold War would make America more powerful than ever, that we had to invade Iraq because Iraq was developing weapons of mass destruction, and that deregulating our economy and signing trade deals would improve the lives of ordinary people. We cannot be surprised that as the scope of those deceptions became clear, people would become angry.

American elites are hardly the only ones who have cynically misled their people. The same happened in Europe. “Ever closer union’’ was another product of the dopey optimism that infected the West in the 1990s. It ignored the evident fact that most Europeans, like most people everywhere, feel loyalty to their own nation or group, and that this loyalty is not easily transferrable to diffuse and distant conglomerations. The EU has been run largely for the benefit of the business class. Ordinary Europeans have come to realize this, and it has angered them. The same anger is enveloping countries from Egypt and Nigeria to Brazil and Venezuela.

In our complex modern age, the interdependent world does not run smoothly by itself. It requires farsighted leadership that takes the fate of ordinary people seriously and favors diplomacy over coercive force. Blaming the masses for stupidly supporting demagogic politicians is mistaken. People quite reasonably resent what their leaders have done to them over the last quarter century. They demand something different, whatever it is. That is the central cause of the new world disorder.

Stephen Kinzer is a senior fellow at the Watson Institute for International Studies at Brown University. Follow him on Twitter @stephenkinzer.