The Marshall Plan was literally the first of its kind in WORLD history. Prior to that, victory in war meant a winner-take-all approach with raping, plundering, pillaging and systematic theft of anything of value (kind of like LA or NYC) or carpetbaggers after the War Between the States.
In short, there is no direct comparison to a singular program on the level of benevolence this country showed to Germany following WW2. You will recall that much of that was in our national interest to stem the Russian expansion through countries "liberated" in WW2 (Poland, Hungary, Czechoslovakia, East Germany, etc) and to ensure that another Hitler wouldn't rise from the ashes.
However, there has unarguably been a steady improvement in the quality of life for descendants of slaves with notable examples being Lincoln's Emancipation Proclamation, end of Jim Crow laws, desegregation of every facet of American life notably including education, the voting rights act, LBJ's war on poverty, etc. If you are seriously going to argue that life as an African American in this country is even remotely like it was following the Emancipation Proclamation, then you are living in another universe than the one in which I live. This nation has spent hundreds of billions of dollars, if not trillions, on programs aimed at black community, more so than Native Americans or Hispanic or Asian or any other minority population group.