After the wave of independence movements swept Latin America in the early nineteenth century, Europe found itself nearly shut out of developments in the entire western hemisphere----even as European countries were colonizing Africa and Asia swiftly and greedily.
To ensure that Europe wouldn't recolonize the Americas, U.S. President Monroe declared in his 1823 State of the Union Address that the western hemisphere was off-limits to European aggression. The United States, of course, wasn't the superpower then that it is today, so it was hardly in a position to enforce its declaration, which became known as the Monroe Doctrine. But Britain, whose navy was enormous and positioned all over the globe, was fearful that Spain wanted to rekindle its American empire, so it agreed to back up the United States. As a result, the European powers continued to invest huge sums of money in Latin American business enterprises, but it didn't make territorial claims. In 1904, after European powers sent warships to Venezuela to demand repayment of loans, President Theodore Roosevelt added what came to be known as the Roosevelt Corollary, which provided that the United States would intervene in financial disputes between European powers and countries in the Americas, if doing so would help to maintain the peace. While Latin American nations have at times benefited from the protection and oversight of their North American neighbor, the Monroe Doctrine also gave rise to anger and resentment in many Latin Americans, who sometimes saw the United States as exercising its own brand of imperialism in the region. This became clear when the United States incited Panamanians to declare their independence from Columbia, so that then the United States could negotiate the right to build the Panama Canalin the Central American nation. Construction began in 1904 and finished in 1914.
In 1898, a European power was dealt another blow in its efforts to maintain a footing in the Western Hemisphere. Spain, which at that time still controlled both Cuba and Puerto Rico, was embroiled in conflict with Cuban revolutionaries when the United States, which sympathized with the Cubans, intervened and launched the Spanish-American War of 1898. In a matter of a few months, it was all over. The United States quickly and decisively destroyed the Spanish fleets in Cuba and in the Philippines, and thereby gained control of Guam, Puerto Rico, and the Philippines. Cuba was given its independence, in exchange for concessions to the United States, including allowing the creation of two U.S. naval bases on the island. The United States, henceforth, was considered to be among the world powers.