The Beginning of American Dominance: From Isolationism to Superpower (1898–1950)

The “American dominion” over the world did not begin with a single event, but through a series of decisive steps between the late 19th century and the middle of the 20th century. Until the 1890s, the United States was a wealthy, fast-growing regional power with virtually no global imperial ambitions and a tiny army (in 1890 it had fewer soldiers than Bulgaria). Just fifty years later, in 1945, it controlled half of the world’s wealth, possessed the only atomic bombs, and had military bases on every continent. Here’s how it happened.

1. 1898: The “Splendid Little War” and the Birth of an Overseas Empire

The turning point was the Spanish-American War of 1898. In less than four months, the United States crushed Spain—a declining European power—and seized:

Cuba (formally independent but effectively an American protectorate until 1959)

Puerto Rico

Guam

The Philippines (after a brutal colonial war against Filipino nationalists, 1899–1902)

For the first time, the United States acquired an overseas empire. Theodore Roosevelt, then Assistant Secretary of the Navy and later president (1901–1909), captured the new mood perfectly: “Speak softly and carry a big stick.” The Great White Fleet (1907–1909)—sixteen white-painted battleships—sailed around the world to display American naval might.

2. The Foundations of the “American Century” (1900–1941)

Between the world wars, the U.S. still practiced political isolationism, but economically it already dominated the globe:

1913: Creation of the Federal Reserve

1920s: Wall Street becomes the financial capital of the planet

1929–1939: The Great Depression hits everyone, but the U.S. emerges with the New Deal and its industrial base intact

Meanwhile, it repeatedly intervened in Latin America (“dollar diplomacy,” then Franklin Roosevelt’s “Good Neighbor” policy): Haiti (1915–1934), Dominican Republic (1916–1924), Nicaragua, Mexico, etc. The Roosevelt Corollary to the Monroe Doctrine (1904) was crystal clear: the United States saw itself as the policeman of the Western Hemisphere.

3. World War II: The Great Leap Forward (1941–1945)

On December 7, 1941, Japan attacked Pearl Harbor. The U.S. entered the war with an economy already recovering and an industrial capacity capable of unprecedented mobilization:

Produced 300,000 aircraft, 100,000 tanks, 88,000 warships

Developed the atomic bomb (Manhattan Project)

Financed the Allies through Lend-Lease ($50 billion in today’s money)

By 1945, Europe and Japan lay in ruins, the Soviet Union was powerful but exhausted (27 million dead), and Britain was bankrupt. The United States had lost “only” 420,000 lives and controlled roughly 50% of global GDP.

4. 1945–1950: Building the American World Order

In just five years, the United States created the institutions that would govern the world for the next seven decades:

1944 – Bretton Woods Conference: the dollar becomes the world’s reserve currency; birth of the IMF and World Bank

1945 – Founding of the United Nations (headquartered in New York, with an American veto in the Security Council)

1947 – Truman Doctrine and Marshall Plan ($17 billion to rebuild Western Europe and keep it from going communist)

1948 – Recognition of Israel and the Berlin Blockade

1949 – Founding of NATO

1950 – Korean War begins: the first “world policeman” war fought mostly (85%) by American troops under a UN flag

So when did American dominance really begin?

It depends on the criterion:Global military reach → 1898 (first modern blue-water navy)

Economic hegemony → 1920s, but definitively consolidated in 1945

Ability to shape the global order → 1944–1949 (Bretton Woods + Marshall Plan + NATO)

In any case, between 1945 and 1950 the United States went from being a great power to the superpower: the only nation with atomic weapons, the world’s reserve currency, the largest alliance network in history, and an economy worth as much as the rest of the world combined.From that moment on, the American Century had truly begun—and it would last (with ups and downs) at least until the 2010s or 2020s.