Final answer:
The most impactful political change during American Imperialism was the significant shift in foreign policy from non-interventionism to active expansion overseas, resulting in the establishment of territories beyond the North American continent, notably after the Spanish-American War.
Step-by-step explanation:
The Impact of American Imperialism
During the period of American Imperialism, the most impactful political change was arguably the shift in foreign policy that led to the United States becoming more actively involved in international affairs and expanding its territories overseas. This marked a significant departure from the previous focus on continental expansion within North America. A defining moment in this shift was the Spanish-American War in 1898, where the U.S. emerged victorious and acquired territories like the Philippines, Guam, and Puerto Rico, marking the beginning of the American empire in the Pacific and the Caribbean.
This era also showcased the United States moving away from the non-interventionist policies recommended by George Washington and shifting towards a more imperialistic approach. This transition reflected a growing belief in American exceptionalism and the country's role in spreading democracy and liberty worldwide. The contradiction between democratic ideals and the realities of ruling an empire spurred significant debate among Americans.
The economic motivations for imperialism also played a substantial role, driven by the U.S.'s rapid growth as a manufacturing power and concern over European competition. The concept of an 'empire of liberty' as envisioned by Thomas Jefferson was used by imperialists to justify acquisitions; nevertheless, the resistance to imperialism highlighted the risks and costs associated with maintaining an empire, as evidenced by the Philippine Insurrection.