Final answer:
The statement that would most likely be made by northerners in the debate over U.S. expansion in the 1800s is that they were concerned about the spread of slavery into newly acquired territories and its impact on the balance of power in Congress.
Step-by-step explanation:
The statement that would most likely be made by northerners in the debate over U.S. expansion in the 1800s is that they were concerned about the spread of slavery into newly acquired territories and its impact on the balance of power in Congress.
For example, the Missouri Compromise of 1820 and the Kansas-Nebraska Act of 1854 were both attempts to address this issue and maintain a balance between free and slave states.
Northerners also argued that expanding the country's territory could exacerbate tension between the North and South, leading to potential conflicts and further division.
Learn more about U.S. expansion in the 1800s