America, until its independence, was a colony of the British Empire, to which, initially there were not any slaves in America, but typically instead there were indentured servants brought here to provide necessary and desired labor help. Great Britain, however, created the Royal Africa company that worked under the aegis of the Majesty of Great Britain, to which one of the functions of the Royal Africa Company, besides the perpetual search for and lust of gold, was the trade in human flesh, to which, part of that process, was to forcefully take Africans from Africa and then export them to either the Caribbean or North America, not as indentured servants, but as human chattel.
Of course, like most government enterprises, there were rules, regulations, taxes, and money involved in this particular trade, so that the government of Great Britain, had a vested interest in the success and the regulation of the slave trade specifically in regards to the Royal Africa Company, to which its British investors of such, demanded a fair return on their money at risk. This meant that each slave brought into America was subject to a tax payable to the Crown for this importation, over and above the actual trading, bargaining and commerce for the slaves themselves. In short, the trading of slaves was not some sort of willy-nilly adventure of arbitrary taking of peoples from Africa, without any rhyme or reason, but something instead that was deliberate, pre-planned, and executed essentially with the stamp of approval of Great Britain as deliberate policy.
While there were plenty of valid reasons why slavery was popular with the planter class, even within that class, at the highest echelon there was an increasing unease with slavery, to such an extent that States such as South Carolina and Virginia, desired to significantly reduce or eliminate the importation of slaves into their respective States, not so much because slavery didn't make economic sense to them, and certainly not because they collectively saw slavery as a blight upon mankind, but primarily because of their anxiety in having so many slaves within their State, that they felt that they were unwittingly sowing the seeds of potential economic destruction, rebellion, uprising, ruin, or revolt, as the sheer amount of oppressed black slave faces in their presence was considered to be quite troubling. In lieu of the continuous importation of slaves, these States, concerned about the unprecedented growth of slavery, hoped to utilize more indentured white servants which would not only more easily assimilate into society but would pose far less of a physical threat than blacks.
In any event, the Royal Africa Company, did not give in to American desires or demands, mainly because the monies that they were making from this trade was quite lucrative for the coffers of the royal treasury, it created steady and dependable profits for its investors, as well as the fact that there were powerful vested interests in America that profited greatly from this trade in human flesh. Had it not been for the Royal Africa Company, there probably would have been far less slavery thrust upon American soil, as the powerful combination of explicit British governmental support, mercantile interests, and the lust for undeserved profits, inevitably led to the wanton trafficking of human subjects from their country of origin in order to be exploited in a country ironically founded upon freedom.