Answer:
D. Exceptionalism
Step-by-step explanation:
A self-perception of its exceptional experience and destiny pervaded the United States in the 19th century before the Mexican-American War, and it got reinforced after that. The vast unexplored territories that laid west were seen a natural target for further expansion after the Louisiana Purchase of 1803. In 1823, president James Monroe proclaims that the US will see as a hostile act any intenvention of European powers in the affairs of Western Hemisphere´s nations: America for Americans. In the following decades, the Manifest Destiny concept guided moves and policies aimed at achieving a territorial expansion westward that was the will of the Providence. The US never faced a powerful river power against which to balance in the hemisphere, two vast oceans provided splendid isolation and a natural barrier against invasion, westward expansion by God´s will as it was believed, and formidable growth and development (after the Civil War); all those factors helped instill a sense of exceptionalism in the American mind.