Because it was a union stronghold in the confederate states.
The U.S changed since the ending of slavery. Slavery was a horror in American History and something that we African Americans take seriously but it also applies to many black and white Americans as well.
Since the ending of the Civil War from 1861 to 1865 which lasted 4 years, black Americans were protected with the 14th amendment but were not equally given equal rights. This was a main issue for blacks and whites and Congress men at that time because they did not know what to do in order for everyone to agree on one specific thing. The Declaration of independence that said "All men are equal" wad a big main topic for Congress leaders and for black people because the founding fathers did not include blacks people in it.
Going down to history the Jim Crow laws and segregation was a big nightmare for black people. Jim Crow law was a law that separated blacks and whites still given "equality" to both sides but not really, because it meant that blacks and whites could not go to public places together and were divided which lead to segregation which impacted many blacks people such as MLK, Rosa Parks, Malcolm X and many to fight for freedom, equality, and justice for all.
Segregation ended finally and black people were happy but whites were not. Many riots where happening in the South and some in the North but that did not stop African Americans from doing more changes that would change American History for ever.
So that is how U.S changed.
*didn't want to go down into details to much so I just said the ones that I knew*
To avoid policies that would draw the U.S into international conflict.
Cuba is what you are looking for.
