In 1861, the United States faced some very difficult issues. These issues divided the nation and the nation soon found itself engaged in a great civil
war.
What is a "civil war?"
1-An argument that is settled by going to a civil court.
2-A violent conflict betwelwn opposing groups within the same country.
3-A war between two countries that share a common border.
4-A compromise between two nations regarding conflicting laws.

3

Explanation:

The American Civil War (April 12, 1861 – May 9, 1865, also known by other names) was a civil war in the United States fought between northern and Pacific states ("the Union" or "the North") and southern states that voted to secede and form the Confederate States of America ("the Confederacy" or "the South").[e] The Union/North side maintained that the secession was invalid, since the union of the states is permanent. Behind this dispute is the primary cause of the war: the South's desire to not only maintain but expand slavery.

i believe that the answer to the question provided above is that  establishing smaller ethnic communities within larger communities  gives more chance for people to know each other more but this might lead to the  conflict between groups.