Not in Vietnam they weren't. Maybe in some other parts of the world.
The United States didn't fight against South Vietnam in fact they were allies fighting against North Vietnam.
To gain more territory for the United States
While fighting communism in Vietnam may have been a good thing, The United States was also supporting an criminally corrupt regime in South Vietnam whic denyed the people of south Vietnam much of their human rights and freedoms for which the United States claimed to be fighting to give them. It is a sad irony that the Vietnamese people actually had more freedom under the communist government than they did under the American backed South Vietnamese government.
The United States wanted the Louisiana territory in order to expand its territory
The land that was given to the United States was known as the Indian Territory.
the United States
The United States withdrew troops from Vietnam, leaving the Republic of Vietnam fighting against the strong Communist force. As a result, Saigon fell into the hands of Communist party.
The United States purchased NO country or territory from Florida (Florida is part of the United States).
The Southern states that formed the Confederate States of American were fighting for independence from the United States of American. The United States (mostly Norther states) were fighting to keep them.
southwest territory
When the Vietnam War started, the world was in the grip of the Cold War. The United States was worried about the possible spread of Communism in Southeast Asia. We felt that we needed to act to prevent this.