What was the main reason slavery was used on plantations in the americas?

Idon't really understand the question. it counts for 20% of my lesson grade and i really need putting the answer into words. anything will . i need asap so im awarding 30 points.a disagreement between states of the united states concerning the rights of states vs. the authority of the national government led to the civil war. state governments were forced by war into a subservient position. what might happen if national governments ceded their authority to a world government by international treaty?

Why did the other allies like great britain and france not support wilsons 14 points?

How is the vietnam war connected to the cold war?