Which effect of the Civil War had the biggest impact on America after the war?
RACE.

The biggest impact of the civil war was the end of slavery.

Explanation:

The southern states had been a little aloof from the US for a long time.

This was partially because f the 'peculiar practice' and many other such things.

These were solved by might and the southern states, albeit with some resentment were brought back into the fold of the union.

At the same time, the south had to give away slavery and then the freed men also became citizens and started having an influence on the policies, albeit a minuscule one.

was a long, primarily nonviolent series of events to bring full civil rights and equality under the law to all americans. the era has had a lasting impact on united states society, in its tactics, the increased social and legal acceptance of civil rights, and in its exposure of the prevalence and cost of racism. in the south violence and fraud in southern elections from 1868 to 1876, which had reduced black voter turnout and enabled southern white democrats to regain power in state legislatures across the south