US Constitution Amendments (14th and 15th) enacted in July 1868 and February 1869 may have been motivation for Blacks to return to the United States

We know that some Blacks did return to fight in the Civil War and after the Civil War with the abolition of slavery in the U.S. in 1865.
*On July 21,1868 the Fourteenth Amendment is ratified, granting citizenship to any person born or naturalized in the United States.
*On February 26,1869 Congress drafts the Fifteenth Amendment; it is ratified on March 30, 1870  granting African American men the right to vote by declaring that the right to vote shall not be denied on account of race, color, or previous condition of servitude.
*Mifflin Gibbs returned to the United States in 1869/1870 and in his autobiography he writes “I had left politically ignoble; I was returning panoplied with the nobility of an American citizen.