Why was it so difficult for the United States to fight Vietnam in the Vietnam War?

The Vietnam War from 1955 to 1975 was a war between the Democratic Republic of Vietnam and the United States against the Democratic Republic of Vietnam and the Southern Vietnam National Liberation Front. The powerful United States, which gained all the benefits in World War II, rose rapidly, but fell into a fierce battle on the land of Vietnam. Nearly 60,000 people died, more than 300,000 people were injured, and the loss exceeded 400 billion US dollars. The war was extremely difficult, and from the result, it didn't gain any benefits. The reason for this is the following：

First, Vietnam. After long-term oppression by French and Japanese colonialists, the Vietnamese people have formed a very strong fighting capacity and resistance spirit in the arduous resistance process, which has been vividly reflected in the fighting between Vietnamese democracy and the international Southern Vietnam National Liberation Front. On the other hand, the Republic of Vietnam, which is supported by the American government, shows that the government is corrupt and infighting, oppressing the people has also lost popular support and its combat capability is weak. America's own troops are useless in the jungles and mountainous areas of Southeast Asia, no matter whether they are sophisticated weapons and equipment or skilled combat methods, and their combat capability is greatly reduced. Therefore, in the early days of the war, the US military did not have an advantage.

The second is the United States. Although the US military is not dominant in Vietnam, the superpower's strength is not timid in Vietnam. However, as we all know, the injustice, huge casualties and tragic war of the United States in the Vietnam War spread to the United States through news and television, and a vigorous anti-war movement was launched in China. A large number of American young men fled to Canada to avoid conscription, and anti-war movements in major cities clashed with the government. The U.S. government's Vietnam War faced enormous domestic pressure. Social chaos has led to the near paralysis of the government, the chaos in the rear of Vietnamese American troops, and the American soldiers abroad are inevitably absent-minded

The third is the world. America's participation in the Vietnam War was to contain the forces in Southeast Asia and launch a war of armed intervention in the Third World. The injustice of the world is obvious to all. On the battlefield in Vietnam, it is not just a contest between South Vietnam and North Vietnam. The tilt of international public opinion has also made the US military slow to move on the land of Vietnam. It can be said that this unjust war for a country's self-interest was doomed to failure from the beginning.