What events led to the war between north vietnam and south vietnam explain american involvement in southeast asia?

The causes of the Vietnam War were derived from the symptoms, components and consequences of the Cold War. The causes of the Vietnam War revolve around the simple belief held by America that communism was threatening to expand all over south-east Asia.

Neither the Soviet Union nor the United States could risk an all-out war against each other, such was the nuclear military might of both. However, when it suited both, they had client states that could carry on the fight for them. In Vietnam, the Americans actually fought  – therefore in the Cold War ‘game’, the USSR could not. However, to support the Communist cause, the Soviet Union armed its fellow Communist state, China, who would, in turn, arm and equip the North Vietnamese who fought the Americans.< https://www.historylearningsite.co.uk/vietnam-war/the-causes-of-the-vietnam-war/ 

The United States Constitution is the main law governing the United States. It was created through the collective effort between the Founding Fathers during the Philadelphia Convention. The main goal of the constitution is to (B) create a national government.

Although amendments are later on added to the constitution, such as the one mentioned in (A), the constitution remained mostly unchanged since its inception.