Final answer:
The Anti-Imperialist League, including members like Jane Addams and Mark Twain, opposed U.S. expansion and the creation of an American Empire following the Spanish-American War, leading to debates in the Senate and public discourse on the future of the newly acquired territories.
Step-by-step explanation:
The group that spoke fiercely against expansion and colonies following the Spanish-American War was the Anti-Imperialist League. Formed in 1898 by a mix of prominent figures like Jane Addams, Mark Twain, and Andrew Carnegie, the league opposed the annexation of territories on a variety of grounds. Some argued it was contrary to democratic principles, some raised concerns over labor competition, while others held xenophobic views about the assimilation of different races.
Their efforts led to a deeply split Senate, with the fate of the Treaty of Paris hanging in the balance. The eventual ratification of the treaty on February 6, 1899, was influenced by fears of an uprising in the Philippines and potential European intervention, giving way to the establishment of the American Empire.
The Anti-Imperialist League's objections mirrored the national debate on whether the newly acquired territories, like Cuba, Puerto Rico, Guam, and the Philippines, would be integrated as democratic states or ruled as conquered lands. The argument against American presence in this nascent empire was that it betrayed the nation's founding ideals of liberty, as evidenced by anti-imperialist criticism of the war in the Philippines. This debate continued into the early 20th century, contemplating the merits and morality of an empire that professed democracy.