What was adopted after the Civil War and has served to not only affect the balance of power in the federal system, but also improve the protection of civil rights and equality for all Americans?

The fourteenth amendment was introduced to protect the laws of all Americans.

Explanation:

After the civil war, everything had been shattered into pieces, the war had left the country into undeniable dilemma about how to move ahead. There were certain laws which protect only certain Americans.

To compensate for the destruction and to adhere to the consequences of the war, a law was passed which did not give African-American laws so that the slaves could go back to being slaves and the destruction caused by the war could be restored.

To protect everyone's right the Americans were introduced to the fourteenth amendment. Which gave them the right to have ownership to land and it safeguarded the rights of its citizens.