That Europeans used the term tribe only to describe African groups
is not correct. As as child I learned that Belgians were a number of
Germanic tribes made of Eburons, Eduoniens, Menapiens, Nerviens and
so on. The word was used also in South America.
I understand the position of African states that desire in the name
of unity to ban the term. Yet, it is certainly useful to describe
specific groups when writing history or anthropology. After all,
Rome, where the word comes from, was divided in four "tribus" (I do
not know the plural of the word, if there is one). Then it just meant
an administrative division!