A few points here:

-Fascism continued to exist long after World War 2; some nations are still fascistic, and others are still recovering (i.e. Spain.)

-Naziism was not defeated to any concievable degree; it was merely pounded into the ground. Its ideas were never refuted; in fact, most of the world quietly agreed with them, despite being at war with the country of Germany itself; and so the ideas continue to live and thrive today. Many countries still quietly celebrate the fact that the Jewish "Problem" was finally solved by the Nazis. Besides, have you ever heard of the "rat line"?

-Communism actually generally benefitted from war. Its only major loss was the Afghan war (which also produced Osama Bin Laden. Yeah, real helpful.)

-The Civil War has many of the same problems as the Second World War; mainly, the "rightwingers" still lived and thrived, as well as having more reason to hate Blacks than ever before. The Northerners also hated Blacks just as much as the Southerners. Besides, it wasn't until the 60's that colored peoples in general were actually seen as being equal to whites, whether in the North or the South.