Well, I believe that they can be wealthy… but the decades why spent as Communists (or, for other repentant nations, Muslims, Atheists, Hindus, etc…) has inflicted real harm in their culture, harm that will take generations to heal.
Sadly, wealth that is built up over generations can be lost in just a decade or two. This is true of families: it is also true of civilizations (See Japan: 1933-1945, or Europe: 1914-1945). Black Americans have lost so much of their culture, familial, and religious strength since the onset of the Welfare State that it’s hard how they will ever get back on their feet, even if the Welfare system dies tomorrow.
(Or even if it dies somewhere in the 2030s, which is actually quite likely!)