The Civil War can be considered the "second American Revolution" in a couple of ways. The Civil War represented a radical shift in how beliefs and convictions would forever be seen in American democracy. Prior to the Civil War, there was not a real discourse as to how the idea of convictions, passionate and non- negotiable values, could be destructive to the fabric of American democracy. The Civil War was a revolution because it radically changed how Americans view their deeply held ideals. John Brown had a conviction that slavery was wrong. It led him to violence. American slave owners had a conviction that slavery was right. It led them to violence. The death and destruction brought on by the Civil War convinced many that no belief can be so valuable when justifies the dissolution of the nation and the death of millions. In this seismic shift of thinking, the Civil War can be seen as America's "second revolution" as it changed the scope of thought about what is essential to the sensibilities of a great democracy.
For people of color, the American Revolution was a "half a revolution." As slavery continued in the wake of the American Revolution, many Americans saw that their lives had not changed. The Civil War changed that. The abolition of slavery and its enshrinement in the Constitution after the Civil War's conclusion proved to be revolutionary for so many Americans. For people of color, specifically Black Americans/ African- Americans, the Civil War was for them what White colonists experienced in the wake of the American Revolution. The idea of self- definition and acting upon one's autonomy becomes the result of the Civil War, helping to make it seen as the "second American Revolution."
The American Revolution was, in a sense, a type of civil war, as the American colonists were considered British Citizens who seceded from their own country.
The American Civil War was similar, in that the people of the South (the confederate States) seceded from their own country to the north (the Union).
It also is be considered a second revolution because African Americans were freed from the overbearing rule of white slavemasters, similar to the way the American colonists were freed from the overbearing rule of the British.