Final answer:
The region of Africa most directly involved in the Trans-Atlantic slave trade was West Africa, where Europeans traded goods for slaves who were then sent to the Americas. The query about tribal migrations and the Confederacy's decline needs further historical context to provide a precise answer.
Step-by-step explanation:
The region of Africa that was most directly involved in the Trans-Atlantic slave trade was West Africa. During the period of the slave trade, European traders built forts and trading posts along the Western African coast where they would exchange goods for slaves. The enslaved Africans were then transported across the Atlantic to the Americas. This tragic part of history deeply affected the demographic and socio-economic structures of West Africa.
In regards to tribal migrations when the Confederacy declined, this could reference different historical contexts, such as the fall of the Confederate States of America during the American Civil War, where the question concerning tribal migrations does not directly apply. However, if this pertains to a different confederacy or region, it would be important to specify the exact historical context for an accurate answer.