A supporter wears a Make America Great Again hat during a campaign rally for Donald Trump in Wilkes-Barre, Pa., last month. (Jake Danna Stevens/ASSOCIATED PRESS)

Donald Trump’s positions on public policy have shifted over the years, months, even days. On Sunday, he managed to express two contradictory thoughts within one sentence: “I don’t want to have guns in classrooms, although in some cases teachers should have guns in classrooms, frankly.” But on one issue he has been utterly consistent: “This country is a hellhole. We are going down fast.” This notion of a country in decline is at the heart of Trump’s campaign and his message — to make America great again.

In fact, it is increasingly clear that the United States has in recent years reinforced its position as the world’s leading economic, technological, military and political power. The country dominates virtually all leading industries — from social networks to mobile telephony to nano- and biotechnology — like never before. It has transformed itself into an energy superpower — the world’s biggest producer of oil and gas — while also moving to the cutting edge of the green-technology revolution. And it is demographically vibrant, while all its major economic peers (Japan, Europe and even China) face certain demographic decline.

Joshua Cooper Ramo, the author of an intelligent new book, “The Seventh Sense,” argues that in an age of networks, the winner often takes all. He points out that there are nine global tech platforms (Google Chrome, Microsoft Office, Facebook, etc.) that are used by more than 1 billion people. All dominate their respective markets — and all are American. The dollar is more widely used for international financial transactions today than it was 20 years ago.

In a pair of essays, scholars Stephen Brooks and William Wohlforth point out that China is the closest the United States has to a rising rival but only on one measure, gross domestic product. A better, broader measure of economic power, Brooks and Wohlforth argue, is “inclusive wealth.” This is the sum of a nation’s “manufactured capital (roads, buildings, machines and equipment), human capital (skills, education, health) and natural capital (sub-soil resources, ecosystems, the atmosphere).” The United States’ inclusive wealth totaled almost $144 trillion in 2010 — 4½ times China’s $32 trillion.

China is far behind the United States in its ability to add value to goods and create new products. Brooks and Wohlforth note that half of China’s exports are parts imported to China, assembled there and then exported — mostly for Western multinationals. The authors also suggest that payments for intellectual property are a key measure of technological strength. In 2013, China took in less than $1 billion, while the United States received $128 billion. In 2012, America registered seven times as many “triadic” patents — those granted in the United States, Europe and Japan.

In the military and political realm, the dominance is even more lopsided. There are many ways to measure this, but take just one: the most potent form of force projection, aircraft carriers. The United States operates 10. China has one, a secondhand Ukrainian ship that it had to retrofit. In the realm of high-tech warfare — drones, stealth — Washington’s lead is even greater. And perhaps most important, the United States has a web of allies around the world and is actually developing new important ones, such as India and Vietnam. Meanwhile, China has one military ally, North Korea.

The complexity of today’s international system is that, despite this American dominance, other countries have, in fact, gained ground. In 1990, China’s share of global GDP was 1.7 percent. Today it is 15 percent. Developing countries as a whole have gone from about 20 percent of the global economy to 40 percent in the same period. And while GDP is not everything, it is a reflection of the reality that no single country — not even the United States — can impose its will on the rest.

I tried to describe this emerging landscape in my 2008 book, “The Post-American World,” in which I wrote: “Washington still has no true rival, and will not for a very long time, but it faces a growing number of constraints.” China has large and growing influence in the world, as can be seen in its ability to create the Asian Infrastructure Investment Bank this past year over Washington’s objections. Rising regional powers such as Saudi Arabia and Turkey assert their own interests in the Middle East, often disrupting U.S. efforts. Even Pakistan, an ally and aid recipient, quietly defies the United States in Afghanistan by supporting the Taliban.

The reality is that America remains the world’s leading power, but it can achieve its objectives only by defining its interests broadly, working with others and creating a network of cooperation. That, alas, does not fit on a campaign cap.

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