The Vietnam War did a tremendous amount to create and heighten social (and political) tensions in the US. It created and emphasized a gap between people who believed in traditional values and those who did not. This gap translated into politics, becoming a partisan issue between Republicans and Democrats.
Traditionally, American patriotism was taken to mean that people should support what the country did militarily, no matter what. The military was seen as an extension of the country, not as something to be argued over and criticized on partisan terms. This belief was not held by the anti-war protestors and other liberals during the Vietnam Era. They felt that the war was wrong and they criticized the government and (less justifiably, at least in my mind) the military that carried out the government's orders.
This helped to create and exacerbate a gap between traditionalists and liberals. It helped to create a sense that the traditionalists (to the liberals) were blind followers, not much better than Germans who went along with the Nazis. On the other side, it helped to create a sense that liberals were people who hated the country that had given them so much in the way of material wealth and rights. This was a huge split and it continues to some extent to this day.
The Vietnam War was unpopular in the United States. Those against it cited a lack of clear objectives, suggesting the war was unwarranted. Although American soldiers who went to war believed they were fighting for the freedom and independence of South Vietnam, the drawn-out conflict stirred dissatisfaction back home. The war required extensive resources both in military equipment and money. The war had serious ramifications for the United States economy; as it drained the country's coffers, the general public began to disapprove of continued support. Divisions emerged between those who believed it was unpatriotic to abandon the war effort and those who could not bear further discomfort and losses for what seemed a pointless conflict. Arguments by civil leaders coupled with student protests sparked outrage.