The Civil War significantly reshaped the U.S. federal system by reinforcing the supremacy of the federal government over the states.

The conflict highlighted the limitations of state sovereignty, particularly regarding issues like slavery and civil rights. Following the war, the federal government took a more active role in regulating states, leading to the passage of amendments that guaranteed civil rights. This shift marked a transition towards a more centralized government, altering the balance of power and establishing a precedent for federal intervention in state matters.