7. Reactions at Home

What was the immediate aftermath in America after the My Lai massacre?
Immediately after the massacre, the U.S. military filed false reports on the event in order to cover up the harsh reality that really happened. The report stated that there were 128 Viet Cong and only 22 civilians, contrary to the approximate 350 deaths, mostly of innocent civilians.(7) The military and federal government first claimed the event to be an accomplishment for the United States in the war. Given this initial information, many Americans felt a sense of pride for the achievement of the troops.(5)

A political cartoon by Paul Conrad about the massacre, showing both sides of America's reactions.
Overall message is that the event distorted America's sense of right and wrong. 

How was the United States military effected?
In addition to the American public's questioning of the military, the massacre impacted the structure of the military as well. A military commission, that was issued as a result of the massacre, discovered widespread failures of leadership, discipline and moral among the Army's fighting units. The incident also changed the way the military issued operational orders during military engagements and exposed significant flaws to the public.(3)

Charlotte Karol
Americans protesting the Vietnam War; one reason why the My Lai cover up was unsuccessful

What were the reactions of Americans after the truth about the massacre was revealed?
Upon the discovery of the true events of the My Lai massacre, America responded with outrage. Americans questioned the conduct of American soldiers in Vietnam after learning about how disorganized the event was. The strong loyalty that Americans had once had for their Armed Forces was hurt by the new image of the military that was created.(13) The war had already been subject to protest before the massacre, so anti-war advocated viewed it as a typical event by American soldiers and proof that the war was immoral. The unfolding of the incident was confirmation for Americans that the war was pointless.
Some Americans felt less badly about the event and defended men like William Calley during their trials. Supporters of the war saw the massacre as some that happens in all ways and saw Calley as a scapegoat for others higher up in military rank.(14) There were many examples of support for Lt. Calley across the nation. The American Legion announced plans that it would try to raise $100,000 for his appeal. Army Draft board personnel resigned in groups in several cities.(13) Those believing the initial verdict against Calley was unreasonable may have helped to convince the federal government to lessen his sentence. 
Some examples of the American media's response to the massacre; placement of guilt was a common topic