The statement that best describes the United States after the American Civil War is that there was a united nation with a new system of government.
A civil war is often known as an intrastate conflict. It is a conflict between organized parties within a single state.
One side's goal could be to take control of the country or an area, win regional independence, or change government policy, and there was the establishment of a new government system after the end of the American Civil War.
Therefore, option A is correct.
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