Wouldn't help. already-successful black Americans would put the money to good use, further separating themselves from the pack and possibly creating a new elite class. Everyone else would probably quickly lose the money to the poor planning and decision-making that inhibits their lifestyles now.
Within a generation, the latter would be talking about how they were set up to fail by conniving whitey and the whole exercise would, at best, be viewed with suspicion and resentment.
And imagine you did really dish out reparations based on colour, regardless of connection to slavery. Chances are, the elite class you'd accidentally be building would predominantly be comprised of Nigerian immigrants. <Lmaoo> You'd end up creating a black-on-black xenophobia problem and justifying the suspicions of people who sympathise with white supremacy.
Talk about cash reparations is like fantasy talk about "if only I could win the lottery" or "if only some rich benefactor would recognise how awesome I am and pay me for existing". Chances are, if you're wishing for it, you're exactly the sort of person who'd waste it.