Eight decades after The London Times accurately predicted the impending collapse of the British Empire, a striking parallel prediction has emerged for the United States’ global dominance, framed against the grinding, stalemated U.S. military campaign in Iran that has laid bare the clear limits of American power.
In a 2026 New York Times op-ed headlined “America Is Officially an Empire in Decline,” contributing editor Christopher Caldwell drew an explicit parallel between 1940s Britain and 2020s America. Back in 1942, at the height of World War II, The Times’ editors already recognized that the sprawling British Empire, then covering a quarter of the globe, had become a “self-liquidating concern.” The temporary advantages that had lifted Britain to global power—unrivaled naval dominance, industrial leadership, and fragmented rival powers—had faded, leaving the empire reliant on coercion to hold restive colonies ready for self-governance. Within five years of that editorial, the British Empire began its rapid dissolution, proving the prediction correct.
Caldwell notes that modern-day America mirrors interwar Britain in key ways: it is deindustrializing, overextended globally, and facing growing fiscal strain. Just as Britain successfully wound down its colonial holdings when it could no longer sustain them, Caldwell argued that Donald Trump, at the start of his second presidential term in 2025, had a historic opportunity to pursue a similar path: shrinking America’s overstretched sphere of influence, refocusing U.S. policy on the Western Hemisphere, and avoiding the fatal overextension that accelerates imperial collapse. Instead, Trump chose to escalate military intervention in Iran, turning what could have been an orderly retreat into a defining turning point that marks the watershed of American imperial decline.
To understand the scope of this shift, it is necessary to examine the deeper structural forces driving the erosion of U.S. global power. For centuries, imperial leaders have clung to the illusion that their realms will endure for centuries, from Hitler’s dream of a thousand-year Reich to the common American assumption that U.S. hegemony is permanent. But modern economic and technological progress has drastically compressed the lifespan of global empires: Britain’s global empire lasted just 90 years, France’s African domain a similar span, and the Soviet bloc in Eastern Europe only 40 years. By this measure, the 80-year run of U.S. global dominance that began in 1945 already exceeds realistic expectations for a modern empire.
The U.S.-led post-WWII global order, built around institutions like the IMF, World Bank, and WTO, drove 80 years of unprecedented global economic expansion. But this very success has sown the seeds of American relative decline: from holding 50% of global GDP in 1945, the U.S. now accounts for just 15% of global output measured by purchasing power parity, compared to China’s 20% and the European Union’s 14%. This decline is not a failure of U.S. policy—it is a testament to the success of the order Washington built, as war-ravaged nations recovered and emerging economies grew far faster than the U.S. over the past eight decades. Today, the U.S. can no longer dictate global economic terms, and must negotiate with a growing array of peer rivals, from China and India to regional blocs like the EU, Mercosur, and ASEAN.
Beyond economic shift, decades of bipartisan geopolitical mismanagement in Eurasia—still the epicenter of global power, home to 70% of the world’s population and the bulk of its economic output—have accelerated U.S. decline. After World War II, the U.S. secured its hegemony by establishing unchallenged geostrategic control over Eurasia, anchoring its influence with NATO in the west and bilateral defense pacts from Japan to Australia in the east, encircling the continent with military bases and naval fleets to contain the Soviet Union. This strategy ultimately led to the Soviet collapse in 1991, but in the three decades since victory, successive U.S. administrations squandered this advantage.
From 2001 to 2021, both Democratic and Republican governments wasted $5.8 trillion on open-ended occupations of Afghanistan and Iraq, costing thousands of American lives, millions of civilian casualties, and creating a power vacuum that China exploited. While Washington was tied down in unwinnable Middle Eastern wars, China’s foreign currency reserves surged from $200 billion in 2001 to $4 trillion by 2014, allowing Beijing to launch the $1 trillion Belt and Road Initiative that has built a sprawling network of infrastructure across Eurasia. By the 2021 U.S. retreat from Kabul, China had already become the dominant power in Central Asia, and America’s geostrategic position on the continent began to crumble.
Trump’s second term has only accelerated this erosion. In the west, his demand that NATO member Denmark cede sovereign control of Greenland created a major rift within the alliance, pushing European powers to pursue more independent trade and defense policies. In the east, the prolonged war with Iran and the resulting closure of the Strait of Hormuz, which disrupted critical Asian oil supplies, strained longstanding alliances with Japan, South Korea, Australia, and the Philippines. Massive missile expenditures in Iran have also forced the U.S. to withdraw missile stockpiles from South Korea and reduce military readiness for Taiwan, leading to widespread questions among U.S. allies about America’s ability and willingness to defend the island against a Chinese incursion. A Chinese takeover of Taiwan would push the U.S. Pacific defense perimeter back from the first island chain to Guam, delivering a fatal blow to American influence in Asia.
The most underrecognized driver of American decline is energy innovation, a force that has shaped the rise and fall of global empires for 500 years. Each era’s dominant energy technology empowered a new leading power: 16th century Spain and Portugal built their empires on the slave plantation system that maximized caloric output; 17th century the Netherlands mastered wind power to build a global commercial fleet; 19th century Britain harnessed coal-fired steam power to conquer a quarter of the globe; and post-1945 America built its hegemony around petroleum, leading to 70 years of repeated intervention in the Middle East.
Today, China is leading a global green energy revolution that is set to reshape the global economy. Solar power is now 41% cheaper and wind power 53% cheaper than the cheapest fossil fuel, and battery innovation is projected to make carbon-based power prohibitively expensive within a decade. While the Biden administration invested $1 trillion to kickstart America’s green energy transition, Trump rolled back those initiatives immediately upon returning to the White House in 2025, canceling offshore wind projects, eliminating electric vehicle tax credits, and opening vast new offshore areas for fossil fuel drilling.
By 2025, half of China’s new power generation capacity comes from solar and wind, China controls 80% of global solar panel manufacturing and 70% of global electric vehicle production. While China’s share of global auto production has risen to 24% and is projected to hit 35% by 2030, Detroit’s share has fallen to just 16% in large part due to Trump’s rollback of EV investment. As China’s low-cost advanced EVs capture global market share, America’s largest manufacturing sector is now fighting for survival, casting a long shadow over the future of U.S. industrial output.
The end of the post-1945 Pax Americana will have far-reaching consequences for the entire world. A post-American global order will almost certainly be more fragmented and more conflict-prone, with no single superpower to enforce international norms and mediate disputes. In the emerging multipolar order, major powers will focus their influence closer to home, while regional blocs like ASEAN, the EU, and Mercosur will take on a larger role in mediating local conflicts. But regional rivalries over borders, water rights, mineral resources, and climate refugees are likely to spawn frequent small-scale regional wars that can cause massive humanitarian harm, as seen in the decades-long conflict in the Democratic Republic of the Congo that has killed more than 5 million people since 1998.
The liberal international principles that anchored the U.S.-led order—human rights, humanitarian aid, national sovereignty, and support for global development—will also fade, even as aspirational ideals. The Trump administration has already abolished the U.S. Agency for International Development, cutting global food and medical aid that analysts project will lead to 14 million extra preventable deaths by 2030, as global governance shifts toward a more transactional order focused on mutual self-interest rather than shared ethical goals.
One of the greatest achievements of the Pax Americana—eight decades without a direct great power war—also faces growing risk. Global military spending is rising rapidly, with nuclear weapons spending jumping 13% in 2023 alone, and the U.S. is set to spend $1.7 trillion modernizing its nuclear arsenal over the next 30 years. As middle-sized powers see that nuclear-armed North Korea avoids the fate of ravaged Iran, nuclear proliferation is likely to accelerate, increasing the risk of accidental or intentional use of these weapons.
For all its flaws and excesses, the American imperial era brought more opportunities for global progress than the great power orders that preceded it, and likely more than any order that will follow it. As U.S. global leadership recedes under the Trump administration, the world will come to miss the Pax Americana. May it rest in peace.