Final answer:
Some American leaders opposed annexing the Philippines over principles, labor concerns, and racial anxieties, combined with profound Filipino resistance.
Step-by-step explanation:
Some American leaders opposed the annexation of the Philippines due to principled, economic, and social concerns. Notable figures such as Andrew Carnegie and Mark Twain, part of the Anti-Imperialist League, feared that imperialism contradicted democratic ideals and could lead to moral degradation.
Economic arguments highlighted the potential flood of cheap labor negatively impacting American workers. Others raised racial and xenophobic concerns, believing that integrating 'alien, inferior, and mongrel races' would damage the national fabric.
Meanwhile, Filipino resistance, led by Emilio Aguinaldo, highlighted the hypocrisy of denying independence after helping to defeat Spain. Ultimately, domestic opposition combined with humanitarian and racial anxieties formed the basis of resistance to Philippine annexation.