It is clear that as the European empires struggled to maintain control over their colonial possessions during the nineteenth and twentieth centuries, the United States searched for footholds in the regions formally under European control. In the nineteenth century, the United States expanded westward and southward absorbing territory which had been held, often loosely, by Spain. In some cases, the United States annexed regions which became part of the union. In other cases U.S. businessmen, or filibusters, simply moved in and dominated the local economies. Due to the Napoleonic Wars and political shifts in Europe, little by little, European interests, or the ability to capitalize on the interests, in the Americas dwindled. Even Great Britain, the great empire of the 1800s, intensified its focus on developing colonial markets in Africa, India, and China rather than the Americas. Certainly the United States was not left alone in the Americas, but it was able to expand its sphere of influence, especially economic influence with greater ease during the nineteenth century and early twentieth century.
While the War of 1812 did not gain the United States territorial holdings in Canada as some had hoped it would, it did establish that the United States was willing to use war as a means to expand, even war with European powers. During the decades following the war, the United States made it very clear to Europe that it intended to be the regional power in the Americas, and that it would not tolerate European interference. Great Britain was actively expanding and defending its worldwide empire, but U.S. Secretary of State John Q. Adams was determined to prevent Great Britain from taking advantage of Spain’s weakened control of territories in the Americas. In a debate with British Minister Stratford Canning in 1821, Adams pointed out that Britain was seeking to gobble up the world markets, even quipping that Britain might have designs on “a piece of the moon.” When the debate circled around to the question of whether the United States still had designs on Canada, Adams replied, “Keep what is yours and leave the rest of the continent to us.”
Shortly after this debate on the expansion of spheres of influence and territorial acquisition, Adams drafted what would become known as the Monroe Doctrine. He encouraged President Monroe to take a bold stand on the issue of European interference in the Western Hemisphere. It did not matter whether it was Great Britain, France, or Russia who had their sights set on a piece of the Americas. The United States declared that it would act to prevent the further exploitation of the Americas by Europe, but that did not mean it would not exploit the Americas for its own benefit. Nor did it mean that it would not seek to spread U.S. political and economic influence beyond the Americas.
During the decades preceding the War of 1812, revolution and independence movements disrupted imperial control, but in the years preceding World War I, a rise in nationalist revolutions set the stage for the demise of the great empires of the previous centuries. Colonialism would be challenged and eventually, after a second world war, eliminated in its previous form. Yet, even as the sun was setting on the colonial system which had helped create the empires of the past, a new colonial structure began to emerge. While the world focused on the war raging in Europe, President Wilson was flexing U.S. muscle in the Americas. Neocolonialism became the policy of a new and emerging empire – the United States. Maybe not an empire in the traditional sense, but an empire in how it used its influence to set economic and political policy favorable to its own national interests rather than the interests of the neighbors it policed. As the great empires of Europe warred and their colonial control declined over the resource rich regions which had once made them powerful, the United States (and later the Soviet Union) expanded a growing economic and political sphere of influence that would rival any traditional empire. In some cases, the sphere would include a military presence or intervention to keep the peace. This was not necessarily a peace that benefited the citizens in the new nations emerging in the wake of decolonization, as much as it benefited U.S. economic interests; but as the United States would remind itself from time to time, peace even a forced peace, was better than war. When the forced peace protected U.S. economic growth and stability, forced peace would certainly, at least to the United States, be the lesser evil, even if it made the United States seem very much a twentieth century empire.
 Walter T. K. Nugent, Habits of Empire: A History of American Expansion, (New York: Alfred A. Knopf, 2008), 73-74.
 George C. Herring, From Colony to Superpower: U.S. Foreign Relations Since 1776, (New York: Oxford University Press, 2008), 134.
 Herring, 386.