Final answer:
The Civil War led to a significant increase in the power of the federal government, affirming its supremacy and expanding its role in governance and civil rights through amendments and legislative measures. The correct choice is that it strengthened the power of the federal government.
Step-by-step explanation:
The impact of the Civil War on federalism is significant, resulting in a heightened dominance of the federal government over the states. Before the conflict, the Articles of Confederation outlined a relatively weak federal government compared to the authority of the states, a power structure that was altered to strengthen the federal level under the U.S. Constitution. The Civil War marked the pivotal point where this balance of power shifted dramatically toward the national government.
Historically, there was a division between those advocating for a strong central government and those favoring state sovereignty. The Civil War resolved this dispute on the battlefield, with the Union's victory affirming the supremacy of national laws and ending the notion of states' rights to secede. The ratification of the Fourteenth and Fifteenth Amendments further cemented the federal government's expanded role, especially in terms of equality and voting rights.
Thus, the correct choice is that the Civil War strengthened the power of the federal government. The increased central power manifested in various ways, including the ability to mobilize resources and citizens for the war effort, the passage of legislation impacting all states, and the imposition of conditions for the readmission of Confederate states into the Union.