USA became a power to reckon with within three decades of end of civil war and heavy Industrialization of USA took place. USA produced 1/3rd of total steel of world by 1900. For a long time, its growth was un-noticed as most of its production was consumed at home itself. It was only by 1890s that it emerged as a colonial power. Its expansion in pacific started in 1880s and it acquired many islands like Hawaiian Islands. It also gained control over part of Samoa Island in Pacific after a tussle with Germany and England. Its domestic production was increasing and like other colonial powers, it was now looking for other markets. In 1893, USA also declared her hegemony over entre American continent and prohibited other powers to interfere in the South America. USA went over war with Spain for control over Cuba and Puerto Rico in 1898. Later she also wrested control from Spain over Phillipines. By 1900, USA had considerable influence in Latin America through rights of military intervention, protectorate or influence. USA also began to influence in internal affairs of Latin American countries purportedly to maintain order and called it as an extension of ‘Monroe Doctrine’.
The Monroe Doctrine was a US foreign policy regarding Latin American countries in 1823. It stated that further efforts by European nations to colonize land or interfere with states in North or South America would be viewed as acts of aggression, requiring U.S. intervention. Its primary objective was to free the newly independent colonies of Latin America from European intervention and avoid situations which could make the New World a battleground for the Old World powers, so that the United States could exert its own influence undisturbed.
The doctrine asserted that the New World and the Old World were to remain distinctly separate spheres of influence, for they were composed of entirely separate and independent nations. USA also gained control over newly built Panama Canal under Roosevelt partly by purchasing shares from French Company which built it, partly by coercing government of Columbia and declaring Panama an independent nation and partly by using money power. Similarly, USA also interfered in affairs of Mexico as well and toppled the government there in 1913 with the help of an aspiring dictator.