Between 1900-1950, The U.S. was emerging as a global power after industrialization, and its foreign policy was deeply intertwined with colonial ambitions and economic expansion. Think imperialism—not in the sense of outright colonies like Britain or France, but through economic control, military interventions, and territorial acquisitions (i.e. the Philippines, Puerto Rico, Guam, interventions in Central America and the Caribbean—“banana republics”).
Policy was guided by capitalist expansion: the U.S. wanted new markets, raw materials, and profitable investments abroad. The U.S. also wanted to stop communism, especially seen in the "Cold War" decades after WWII (1950s -1980s).
The rhetoric of “spreading democracy” often masked economic and strategic goals, tied directly to the legacy of European colonialism.
By mid-century, the U.S. starts confronting communism, but it’s mostly European fascism first seen in WW II. The U.S. emerges as a global hegemon not just militarily, but economically, consolidating a capitalist world order after the Allied victory of WW II.
Now circa 2000, the U.S. operates in a postcolonial world, where most territories are formally independent, but economic and military influence maintains neocolonial patterns. Think Iraq, Afghanistan, Africa, Latin America—interventions framed as “democracy promotion” or “counterterrorism” but often serve corporate interests, resource access, and geostrategic dominance.
The Cold War lens of capitalism vs. communism shifts into capitalism vs. regional powers and terrorism, but the global capitalist project is paramount. China’s rise brings back elements of ideological competition, but now it’s a more nuanced capitalist rivalry than outright communism vs. capitalism.
Policy is highly justified through soft power, international institutions, and multilateralism, but the underlying logic is still economic domination and securing global markets—a postcolonial form of influence, rather than direct territorial control.
In short,
A) Early U.S. 20th century foreign policy was 1) direct or quasi-direct colonial control 2) capitalism expansion 3) anti-communism (mostly theoretical yet evolved into the the mid-20th Century 'Cold War' and proxy battles seen in Vietnam and Korea)
B) Early U.S. 21st Century was/is 1) indirect/neocolonial control 2) postcolonial world framework 3) capitalism remains the engine 4) communism mostly replaced by corporate rivals 5) terrorism or 'rising powers,' interventions framed as “humanitarian” or “security” missions.
Basically, what you notice is that historians rarely frame U.S. policy in terms of capitalism and postcolonial power structures, even though these forces are the connective tissue from the 1900s to today. Colonialism evolves into neocolonialism, but the economic logic—profiting off global labor, resources, and markets—remains. Also, what connects 20th and 21st Century U.S. foreign policy is the country's desire to spearhead the globe and collaborate more with nations around the world vs. isolationism and staying within the borders. You can see this today with the emergence of Trumpism, xenophobia, and anti-immigrant sentiment from the "Make America Great Again" movement and today's rise of American fascism.