B the 15 amendmentgave freed slaves suffrage or the right to vote
Some examples of this were the Fugitive Slave Act, Preston Brooks's attack on Charles Sumner, and the Dred Scott decision (the part of it which said that African Americans could never be citizens). None of these events tangibly hurt the North or the South.
A state of political and milatary tension after world war 2 between powers in the western Bloc
A tariff on imported goods can lead to lower un employment through increased consumption pf domestic production.