No revolution, social or otherwise starts overnight. For most social revolutions in 60s, the spark was long in place before WWII came, but found itself greatly assisted by the war and the post war period. For race relations in America, the Double V campaign was a real eye opener for Americans. Blacks, just like everyone else, were being drafted to fight in a war sold as a defense of liberty and freedoms--that many of them, especially those living in the segregated South did not enjoy. Organizations like NAACP (founded 1909) were also quick to point out the hypocrisy found within the US.

Women's suffrage and prohibition after WWI, Reconstruction (including the 13th-15th amendments) after the Civil War. I don't really know what you mean by "similar things didn't happen after previous major wars"