I was speaking to the change in society, not to the effectiveness of the policies. The number of valor awards from the 442nd pretty much puts any debate on that issue to bed.
If you're talking about social cohesion, that tends to vary throughout history, generally based on economic conditions. I'd argue that the Civil War era which you cited before was a time of extremely low social cohesion, so much so that the Union itself split apart and significant portions of the population in both North & South were actively disloyal or aggressively nonparticipatory in the war itself. The WWII era had a much higher degree of social cohesion, but that was also a function of the industrial economy and its subsidiary, national conscription.

The WWII era was not more virtuous than today. It was vastly less egalitarian and unequal politically, saw violent and aggressive disenfranchisement of large segments of the American population, and from a purely military standpoint oversaw enormous incompetence and disasters which were either covered up or disregarded in the name of national morale (Market Garden, Pearl Harbor, the fall of the Philippines, Hurtgen Forest, the failure of Army commanders at Omaha to take advice from Pacific theater veterans, much of the Italian campaign, etc. etc.) IMO we need to stop looking at the past in sepia tone and understand it for what it really was - that's the only way to gain both understanding and lessons for the future.