RECOMMENDATION: Please watch this video and then read the superb essay by John Gerassi on the same topic, analysing the gradual development of US imperialism and its poisoned fruit across the globe.

Violence, Revolution, and Structural Change in Latin America (Revised and expanded)
This essay, by a respected radical, packs many gems, to wit:
"The basic difference between American imperialism today and American imperialism a century ago is that it is more violent, more far-reaching, and more carefully planned today. But American foreign policy, at least since 1823, has always been assertive, always expansionist, always imperialist. Of course, it has rarely been pushed beyond America’s capabilities. Thus, when the United States was weak, its interventions abroad were mild. When its strength grew, so did its daring. Today, as the most powerful nation on earth, with a technological advance over other countries of mammoth proportions, the United States can be imperialistic on all continents with relative security..."

or

A liberal, but not an American, Salvador de Madariaga, once explained its hold on Americans:

I only know two things about the Monroe Doctrine: one is that no American I have met knows what it is; the other is that no American I have met will consent to its being tampered with. That being so, I conclude that the Monroe Doctrine is not a doctrine but a dogma, for such are the two features by which you can tell a dogma. But when I look closer into it, I find that it is not one dogma, but two, to wit: the dogma of the infallibility of the American President and the dogma of the immaculate conception of American foreign policy.