Whose Responsibility is it to rebuild America after the Civil War

The responsibility lay with the United States government.

Explanation:

That period in the history of the United States is known as the Reconstruction Era. The government's biggest challenge is the integration of the Southern states into new political, social and economic trends. The south of the country was lagging in industrialization, so it was necessary to involve that part of the state in American everyday life. The government also faced the problem of freed slaves, which needed to be integrated into American society. The process of social integration of African Americans into society has been rather slow. Many destroyed infrastructure and material goods were found in the country, so the government had to start rebuilding.

explanation:

the declaration states, “we hold these truths to be self-evident, that all men are created equal, that they are endowed by their creator with certain unalienable rights, that among these are life, liberty, and the pursuit of happiness….”