Why did the USA lose the Vietnam War?

The Americans did not lose purely for military reasons. There were other factors as well.

Write an explanation AND cite a source which shows the importance of the following six factors:

1. US military tactics in Vietnam
The US did not use guerilla warfare, while Vietnam did.

2. The unpopularity of the South Vietnamese regime
People didn't respect the South Vietnamese regime because it was capable of remaining strong, it would get pushed around and do nothing.

3. The experience of the Viet Cong and the inexperience of the American soldiers
The Viet Cong had the home advantage and they had good military tactics, while the americans were just coming in and unexperiencingly killing people, including many innocent people.

4. Domestic opposition to the war in the U.S.
The US citizens didn't see the purpose to the war. They just saw monks burning and innocent people and children being slaughtered by the americans.

5. Chinese and Soviet support for the Viet Cong
The Communist countries like the Viet Cong because of their communism, so this made them stronger.

6. 'But did they really lose?' Summarize the argument put forward in Source 57, and your view on it.
They didn't lose, even though america did back out of vietnam, it was only because it was unfavorable to the american public.
Add other if you think there are factors you should consider.