During many years of the Vietnam War about 100 GI's a week were killed. During Tet over 500 were killed every week. Years of casulties took its toll on the home front. 20+ years earlier America mobilized, fought and won a world war in 3 & 1/2 years. What seemed to many to be an endless war became too much. I get that.
During World War II an average of 2,000 Americans were killed every week in the defense of Europe alone. The difference was that we were allied with the Russians in WWII and the American communists kept their mouths shut but during the Vietnam war the American communists were uninhibited in their opposition.
From the outset of the war in Europe the political leadership in the U.S. was committed to full mobilization and all out war while the leadership during the Vietnam war tried to fight a limited war with partial mobilization. The results were disastrous.