Barack Obama’s presidency marks the decline and fall of America as the world’s last superpower; it is the end of the American moment, the period from 1945 in which the United States walked on the world stage like a military and economic colossus. Like ancient Rome, America has lost its civilizational will to maintain its great-power status. The country has become stripped from its Judeo-Christian moorings and founding principles. Our liberal ruling elites no longer believe in American exceptionalism or its historic mission as the defender of democracy and liberty.

This was evident during Mr. Obama’s recent trip to the Summit of the Americas, the gathering of all the heads of state in the Western Hemisphere. Instead of championing American national interests and values, the celebrity-in-chief rushed to cozy up with Latin America’s two worst dictators: Venezuelan President Hugo Chavez and Cuban strongman Raul Castro (the younger brother of the ailing Fidel). Mr. Obama engaged in several high-profile photo-ops with Chavez, publicly shaking his hand and calling the Bolivarian despot his “amigo.” Mr. Obama’s actions disgraced the United States, undermined human rights and emboldened the region’s leading anti-American demagogue to further export his brand of revolutionary socialism.

Mr. Chavez has dismantled Venezuela’s democracy. His regime routinely murders and imprisons political dissidents, cracks down on media freedoms and systematically harasses opponents—including leading members of the Catholic Church. He has centralized power, using class warfare to decimate the country’s middle class and erect an authoritarian socialist state. He is following the Marxist model of Castro’s Cuba.

Moreover, Chavez has emerged as the region’s most dangerous threat to U.S. security interests. He is using Venezuela’s vast oil wealth to prop up anti-American, socialist autocracies—like Bolivia and Cuba. His regime funds the leftist FARC terrorists in neighboring Columbia. He actively supports drug trafficking—especially, into the United States, poisoning our nation’s youth. He has fostered close ties with Iran’s mullahs, backing their drive for a nuclear bomb.

Yet, Mr. Obama refused to stand up to this tin pot dictator. He didn’t defend Chavez’s countless victims, who are rotting in the jails of Caracas. Instead, the leader of the free world sent a powerful signal: Washington prefers being liked by odious regimes than champion human rights and democracy. Mr. Obama’s cowardly actions betrayed not only the suffering people of Venezuela, but fundamental American principles.

On Cuba, Mr. Obama is slowly tilting toward a policy of engagement and appeasement. He has relaxed prior policies on remittances and travel to the island dictatorship. Telecommunications companies are lining up to do business with Castro’s apparatchiks. But Castro is not interested in opening up Cuba’s political system and economy: any such moves would result in the same thing that happened in the former Soviet bloc—the collapse of communism.

Mr. Obama’s embrace of Chavez and Castro should come as no surprise. Like them, our celebrity-in-chief is a transnational socialist, who believes America is to blame for much of the globe’s problems. He shares many aspects of their worldview—state control over the economy, soak-the-rich redistributionist policies, massive public spending, a neutered U.S. foreign policy, direct diplomatic negotiations and closer ties with Iran, China and Russia, and the end of an American unipolar international system. Mr. Obama, of course, is a democrat; they are tyrants—and that is a fundamental and all-important difference. He can be replaced at the ballot box; they can’t.

But Mr. Obama is a revolutionary leftist, who is slowly transforming America into a post-modern, post-national, nanny state. In foreign affairs, he has gone to Europe and apologized for the United States’ past “arrogance—despite the fact that, at tremendous cost in blood and treasure, it was America that liberated the continent from Nazi occupation and the menace of Soviet totalitarianism (During the 1990s, while genocide was taking place on their doorstep in the Balkans, the Europeans did nothing until—you guessed it—Uncle Sam intervened). Mr. Obama seeks a rapprochement with Iran’s apocalyptic Islamist mullahs. He has called for unilateral nuclear disarmament. He has failed to punish North Korea for its illegal missile launch. He is back-pedaling on Washington’s pledge to install missile-defense sites in Poland and the Czech Republic in order to pacify Russia’s revanchists. And he has publicly demanded that Red China be treated on an equal footing with the United States, elevating the status of a belligerent, militaristic and ultra-nationalist regime to the level of a co-equal hyperpower. In short, he is systematically undermining America’s international prestige and standing, attempting to erect a multi-polar world order—where America is only one of many great powers.

At home, Mr. Obama is implementing the most ambitious leftist agenda in our history. He has passed a nearly $1 trillion stimulus package. His administration is nationalizing the big banks and the insurance companies. They are bailing out key sectors of the economy—including the automakers, to the point where Washington is picking who runs General Motors. He supports government-run health care, federally subsidized day care, pouring billions into public works projects, expanding funding to unemployment insurance and Medicaid, granting amnesty to 12-20 million illegal immigrants, creating a new “green economy,” mandating draconian cap-and-trade environmental regulations and imposing a nearly $1 trillion tax increase. The non-partisan Congressional Budget Office states the Obama administration will add $9.3 trillion to the national debt over the next ten years—accumulating more red ink than all the previous 43 administrations combined. The Federal Reserve is printing money to underwrite these massive levels of deficit spending and government commitments. Bailout Nation is leading to Bankrupt Nation. No country can sustain this kind of fiscal irresponsibility and social engineering—not even the land of milk and honey.

America is not immune to the laws of economics or history. Civilizations rise and fall. Our Founding Fathers understood this; in fact, they were deeply learned students of history. Their entire mission was to erect a republic—an experiment in individual freedom and self-government—that would endure the test of time. Upon leaving the Constitutional Convention, Benjamin Franklin was asked, “What kind of government have you given us?” Franklin’s response: “A Republic if you can keep it.” We are, however, in the process of losing our republic. We are going the way of ancient Rome.

Rome collapsed because of internal decay and the abandonment of its animating principles. It was the great superpower of its age, spreading peace, order, commerce, art, literature, culture, roads, prosperity and the rule of law. Yet, over time, its civilizational will to lead and survive was sapped. It no longer could protect its borders. Its politics was slowly undermined by factionalism, vicious infighting and the relentless centralization of power. It no longer could stand up to its external enemies. Patriotism and civic virtue were gradually extinguished. Its economy was strangled by crushing taxation and a burdensome, bloated bureaucracy. Sexual permissiveness, obsession with fame and entertainment, homosexuality and hedonism became rampant. The Romans lost more than their self-respect. They lost their sense of historical patrimony: What it meant to be a citizen, and the sacred rights and responsibilities that came with it. Their civilization slowly crumbled and died—going out not with a bang, but a pathetic whimper.

The Obama presidency represents an historic watershed: The time in history where the United States repeated the tragic pattern of Rome. We now have a commander-in-chief, who no longer believes in the American mission or in the foundational values that propelled the United States to global preeminence—limited government, free-market capitalism, traditional morality, national sovereignty, a distinct cultural identity and the unrivalled champion of freedom, democracy and human rights. His socialist internationalism not only emboldens our enemies, such as Chavez and Castro, but signals the loss of American power, American will and American self-confidence. Obama’s America is characterized by national confusion, moral self-loathing and civilizational paralysis. Once those qualities enter the bloodstream of a body politic, they are almost impossible to cure. And they lead to only one end: decay, decline and eventual ruin. It happened to Rome. And it is happening to us.