Answer:
War would weaken the United States' power in the Western Hemisphere.
Step-by-step explanation:
European powers favoured the Civil War of the 1860s because they wanted a weakened hold of the United States in the Western Hemisphere. A split in the United States (Union and Confederate) indeed pleased the European countries, because it would break the Monroe Doctrine. The doctrine threatens European nations that the United States would not allow more colonization and monarchs rule in the Western Hemisphere.