> the West African tribes often sold the slaves to Europeans

I think that you are being disingenuous here. The African tribes that sold slaves were not necessarily the slave’s own tribe, but rather a different tribe that proved victorious in war or raiding. The slave’s own tribe, as I mentioned, would hardly have been unable to ransom its own people from the US due to lack of literacy, lack of communications, and lack of financial means. Meanwhile, postal connections between North Africa and Europe were reliable enough by the 17th and 18th centuries that slaves could message home for ransom, and this was frequently allowed as it proved highly lucrative for Barbary slaveholders.

> white slaves in a non-white country

This is a completely ahistorical way of describing the matter. In terms of race linked to skin colour, Barbary slaveholders very much considered themselves white in opposition to the black African populations to the south whom they exploited. (This survives in modern Mauritanian slaveholding.)

Moreover, Muslim slaveholding here and in the broader region was bound up with with issues of religion, not race as the modern USA understands it. In as little as a single generation post-manumission, those descendants of raided European slaves were no longer necessarily regarded as an outcaste, provided they were observant Muslims, which is why so much of the power in the Ottoman Empire famously ended up in the hands of men of Eastern European descent. At least in terms of knowing your progeny would be better off, they had privilege that African chattel slaves in the USA could only dream of.

Moroccan black slave status being by descent was majorly opposed by the ulema there