Colonies were forced to import cheap manufactured goods.
What you basically need to know is that the contras were right-wing and that they opposed the left-wing government.
The left-wing governments were generally not seen as desired during the cold war because they could strengthen the communists, which were competing with the US.
So the US hoped that the contras would weaken or even replace the left-wing government.
Answer:
One major log to the fire is the Civil War. The south was with slavery vs. the north who were fighting to abolish it.