What were the positive and negative consequences of American wartime propaganda?

Throughout American Military History, there have been positive and negative consequences alike that follow from the use of wartime Propaganda. One undeniable positive (seen, for example, during World War I) has been the stimulation of 'war spirit' among Americans. One undeniable negative (seen, for example, during the Vietnam War) has been tremendous demoralization and even hostility towards the government when the war-reality has turned out to be different from the propagandistic account of the war.