The Civil War in the United States is a collection of articles and letters from Marx and Engels that follows the whole war.

Black Reconstruction in America by WEB Dubois is essential reading

I feel comfortable being blatantly sarcastic here lol. I've been telling people to read The Civil War in the United States by Marx for years on this site.

Obviously the US Civil War had an effect on the revolutionary consciousness of the world. English workers were actively organizing against the textine owners and holding rallies/striking. Marx was running around documenting the working class movements in the North and in England.

The positions of the Abolitionists were later absorbed by many Communists, and expanded on with the concepts of Wage Slavery. The black revolutionaries in America all built their consciousness in the context of the Civil War.

Reconstruction is used frequently as an example of liberal failure and the need for an organized vanguard ("tankies") to solidify the gains of revolution.

Lenin's dual revolution idea was derived from the failure of the American workers and liberated slaves to sieze power.