During the height of the African slave trade before the American Revolutionary War, why were slaves also not shipped to European countries like England, France, Spain and others as well as the various ports in the Americas?
This is a question of historiography misleading us. There were indeed black, African slaves in late medieval and early modern Europe. They were quite popular in southern (Spain, Italy, Austria) courts as part of a show of power. Maria de Luna, queen of Aragon over the turn of the 15C, gave a "little black girl" slave named Sofia to the king of Navarre, while the king of Sicily 'gifted' two adult female slaves, Rosa and Dominica, to Maria. Household accounts record who was in charge of keeping Rosa and Dominica fed and adequately clothed--indeed, it seems that the outfits worn by the slave women were vital details to record, since their well-adorned presentation was an important part of Maria's displays of status for herself.
The books of essays Black Africans in Renaissance Europe has more stories like that of Maria, Sofia, Rosa and Dominica, if you are interested in learning more.