So here's how that would play out, Day 1 - Black folks sell their US citizenship for $5M; Day 2 - Trump & Co. announce that the American dollar is now worthless. From here on, America runs on Dunkin (or TrumpCoin or whatever).
So now black folks have rescinded their citizenship and they have about $5M worth of tissue paper on whatever tropical island they decide to retire to. Congratulations, you played yourself. And to make matters worse, the American oligarchs have officially declared climate change a "woke hoax", so it's very likely within a generation hurricane season is gonna flip that little island you call home upside down.