Answer:
The United States wanted to influence the world to protect democracy.
Explanation:
If the response is that
The domino theory led to conflict in Vietnam
the idea to be included in the response has to be the one mentioned above.
The domino theory was an American Cold War theory that said that Communism (threatening democracy) would spread through Asia as countries falling as domino stones for communism.
This theory formed part of the influential US foreign policy in order to protect Western democracy throughout the world.