While the Civil War was fought between states of the same country, the Revolutionary War was technically fought between two separate countries: the colonies declared independence from Great Britain one year into their conflict, while the South never issued an official Declaration of Independence.
Technology was more advanced in the Civil War than the Revolutionary War, making the killing of hostile soldiers easier, which in turn ensured a huge difference in casualties: less than 100,000 soldiers died on the battlefield during the Revolution, while 617,000 soldiers died in battle during the Civil War.
Tactics in the Civil War and the Revolutionary War were different: in the Revolutionary War both armies would march onto the battlefield and fire at one another from a short distance away, exchanging volleys until one side ran out of soldiers or ammunition. In the Civil War, tactics were more flexible depending on the battlefield and on the size of the opposing force.
During the Revolutionary War outside forces became involved in the war: the British deployed German mercenaries in battles against the Americans, while the French and the Spanish fought on the side of the Americans after the Americans won the Battle of Saratoga in 1777. No other forces ever became involved in the war between the North and the South: all the troops deployed in the war were American citizens.
During the Civil War ironclads were deployed, while wooden warships were used throughout the Revolutionary War.
