What were some of the effects of American annexation?

The American annexation of territories, particularly after the Mexican-American War, led to significant demographic, cultural, and political changes. It expanded the U.S. territory significantly, fueling debates over slavery and states' rights that contributed to the Civil War. Additionally, it resulted in the displacement and marginalization of Indigenous populations and Mexican citizens, altering their social and economic landscapes. The annexation also played a crucial role in shaping America's identity and its trajectory as a continental power.