With most Americans believing that the United States is in decline, Donald Trump claims he can "Make America Great Again." But Trump's premise is simply wrong, and it is his proposed remedies that pose the biggest threat to America.

Americans have a long history of worrying about decline. Shortly after the founding of the Massachusetts Bay colony in the seventeenth century, some Puritans lamented the loss of an earlier virtue. In the eighteenth century, the founding fathers studied Roman history when considering how to sustain a new American republic. In the nineteenth century, Charles Dickens observed that if Americans are to be believed, their country "always is depressed, and always is stagnated, and always is at an alarming crisis, and never was otherwise." On a 1979 magazine cover about national decline, the Statue of Liberty has a tear rolling down her cheek.

But while Americans have long been drawn to what I call the "golden glow of the past," the US has never had the power many imagine it did. Even with preponderant resources, America has often failed to get what it wants. Those who think that today's world is more complex and tumultuous than in the past should remember a year like 1956, when the US was unable to prevent Soviet repression of a revolt in Hungary; and when our allies Britain, France, and Israel invaded the Suez. To paraphrase the comedian Will Rogers, "hegemony ain't what it used to be and never was." Periods of "declinism" tell us more about popular psychology than about geopolitics.

Still, the idea of decline clearly touches a raw nerve in American politics, making it reliable fodder for partisan politics. Sometimes, anxiety about decline leads to protectionist policies that do more harm than good. And sometimes, periods of hubris lead to overreaching policies such as the Iraq War. There is no virtue in either understatement or overstatement of American power.

When it comes to geopolitics, it is important to distinguish between absolute and relative decline. In a relative sense, America has been in decline ever since the end of World War II. Never again would it account for half the world economy and hold a monopoly on nuclear weapons (which the Soviet Union acquired in 1949). The war had strengthened the US economy and weakened everyone else's. But as the rest of the world recovered, America's share of global GDP fell to one-third by 1970 (roughly its share on the eve of WWII).

President Richard Nixon saw that as a sign of decline and took the dollar off the gold standard. But the greenback remains preeminent a half-century later, and America's share of global GDP is still about one-quarter. Nor did America's "decline" prevent it from prevailing in the Cold War.

Nowadays, China's rise is often cited as evidence of American decline. Looking strictly at US-China power relations, there has indeed been a shift in China's favor, which can be portrayed as American decline, in a relative sense. But in absolute terms, the US is still more powerful and is likely to remain so. China is an impressive peer competitor, but it has significant weaknesses. When it comes to the overall balance of power, the US has at least six long-term advantages.

One is geography. The US is surrounded by two oceans and two friendly neighbors, while China shares a border with 14 countries and is engaged in territorial disputes with several, including India. A second is relative energy independence, whereas China depends on imports.

Third, the US derives power from its large transnational financial institutions and the international role of the dollar. A credible reserve currency must be freely convertible and rooted in deep capital markets and the rule of law - all of which China lacks. Fourth, the US has a relative demographic advantage as the only major developed country that is currently projected to hold its place (third) in the global population ranking. Seven of the world's 15 largest economies will have a shrinking workforce over the next decade; but the US workforce is expected to increase, while China's peaked in 2014.

Fifth, America has long been at the forefront in key technologies (bio, nano, information). China is investing heavily in research and development - it now scores well in terms of patents - but by its own metrics, its research universities still rank behind US institutions. Lastly, international polls show the US outranking China in the soft power of attraction.

All told, the US holds a strong hand in the twenty-first-century great-power competition. But if Americans succumb to hysteria about China's rise, or to complacency about its "peak," the US could play its cards poorly. Discarding high-value cards - including strong alliances and influence in international institutions - would be a serious mistake. Far from making America great again, it could greatly weaken it.

Americans have more to fear from the rise of populist nationalism at home than they do from the rise of China. Populist policies, such as refusing to support Ukraine or withdrawing from NATO, would do great damage to US soft power. If Trump wins the presidency in November, this year could be a turning point for American power. Finally, the sense of decline might be justified.

Even if its external power remains dominant, a country can lose its internal virtue and attractiveness to others. The Roman empire lasted long after it lost its republican form of government. As Benjamin Franklin remarked about the form of American government created by the founders: "A republic if you can keep it." To the extent that American democracy is becoming more polarized and fragile, it is that development that could cause American decline.

From Project Syndicate