Which of the following is not a reason why the U. S decided to declare war in Vietnam

D. The U.S did not want Vietnam to be ruled by the French

Explanation:

A is true due to the "Red Scare" if communism spreading across the world

B is true since the U.S were not in good terms with the USSR, and the fight against communism was prevalent in Soviet Controlled countries

C is true, some research done today has found evidence to suspect that the U.S government misinterpreted the information to justify a war against Vietnam (this is why the question says "allegedly")