What was a common rationale used by supporters of U.S. imperialism?

Supporters of U.S. imperialism often justified their actions through the belief in the racial superiority of Americans, which was rooted in the ideology of Manifest Destiny and Social Darwinism prevalent during the late 19th and early 20th centuries. This belief posited that it was the United States' inherent right and destiny to expand its territory and influence, spreading what they considered superior American values and culture to other nations and peoples deemed "less civilized." This rationale was used to legitimize the annexation of territories, interventions in foreign nations, and the imposition of U.S. governance on diverse populations.

The other options reflect different perspectives on imperialism or national interests. Economic self-sufficiency and the encouragement of global trade partnerships relate to strategic or economic motivations, which were certainly present, but they do not encapsulate the widely shared ideology that justified imperialist actions in a racial or cultural context. The promotion of civil rights for all contrasts sharply with the imperialistic mindset, as many imperialist actions were marked by oppression and the denial of rights to the people in the annexed territories. Hence, the belief in racial superiority stands out as a central justification for the imperialist ambitions of the United States during this period.