Which problem did the U.S. military face as it attempted to carry out the war in Vietnam?

The U.S. military faced significant challenges in the Vietnam War, primarily due to the guerrilla tactics employed by the Viet Cong and North Vietnamese forces, which rendered conventional military strategies less effective. The dense jungles and difficult terrain complicated operations and limited visibility. Additionally, the lack of clear political objectives and growing anti-war sentiment in the U.S. created further obstacles, undermining morale and public support for the war effort.