The question of reparations came up in the 1890's. At that time the members of the G.A.R - Grand Army of the Republic. told the former slaves that they had gotten all they would from them. The G.A.R. was talking to actual former slaves.
I have run the numbers. Starting with April 1861 and going to April 1865, the Union Army lost 77 combat dead a day, every day. The Union states were 20 million people at the time. If the same ratio of soliders died in Viet Nam, the Wall would have about 1 million 50 thousand names on it.
America has paid its debt in the blood of those brave men.
Case closed.
There, done. what was so hard about that?