Final answer:
The rapid spread of slavery in the American colonies was primarily driven by the profitability of growing cash crops with enslaved labor and the existing prevalence of slavery in the Caribbean.
Step-by-step explanation:
The main reasons for the rapid spread of slavery in the American colonies were:Colonists found that they could profitably grow cash crops with enslaved labor. The demand for labor to grow New World cash crops, such as sugar and tobacco, led Europeans to increasingly rely on enslaved Africans. Africans were considered physically better suited for hard labor and could be enslaved for a lifetime, ensuring a constant supply of field hands.Slavery was already common in the Caribbean when rice was introduced in South Carolina. Many settlers in North America began importing African slaves to make up for the shortfall in cheap labor. Slavery became more prevalent in the southern colonies, especially in South Carolina, where rice plantations flourished.