Slaves were brought in America from Africa. Getting slaves from Europe was difficult because slavery was not a very well managed in Europe. Africa on the other hand was a thriving market place for slave buyers. The local economy in Africa facilitated buying and selling of humans.
There is another reason as to why African laborers were preferred over other regions. The laborers had to work in plantations where malaria and yellow fever were quite common. These diseases had originated in Africa and therefore the African slaves had gained a genetic immunity against these diseases. While European/Local American population of slaves died in droves, succumbing to the malaria, African laborer were immune to these diseases.
However, this did not translate to them being socially uplifted from poverty and ignorance. Their status remained of an impoverished section of the society. After all they were slaves! Something that could have been a huge advantage for a community resulting in its prosperity turned out to be the very reason for African slavery businesses to flourish.
Ah ! The cruelty of fate ..
Writings inspired from Sapiens by Yuval Noah Harari.