The correct answer to this open question is the following.
Although there are no options attached we can say the following.
Explain how "the wealthiest and most powerful nation in the history of the world made a maximum military effort with everything short of atomic bombs, to defeat a nationalist revolutionary movement in a tiny, peasant country-and failed."
The reasons are the following.
The United States had established the foreign policy of containment during the Cold War years to stop the spread of communism. It was the time in which the United States competed with the Soviet Union in the arms race, the space race, and the spread/containment of communism.
North Vietnam was supported by the Soviet Union, which is why the United States helped South Vietnam and got into the Vietnam War.
However, it was not a United States war, and the country never committed to that. Yes, the federal government sent troops, supplies, machinery, aircraft, and weapons, but experts said there was never really a sound strategy to fight in that complicated territory.
The US Army invaded a foreign territory, a jungle, one with many complexities: geographic, weather, and strategical complexities
The Tet Offensive was considered the turning point in the Vietnam War in that it convinced Americans that the war wasn't nearly over.
The North Vietnam army launched a series of attacks over South Vietnam's positions. It was known as the Tet Offensive and served to send a message to the United States troops that this war was not theirs. When US citizens watched the news they started to question US participation in the Vietnam War. Groups of students and civil rights movements took the streets in major US cities to protests against the war.