Why did the American public call for an end to the Vietnam war?

The communists' Tet Offensive of 1968 crushed U.S. hopes of an imminent end to the conflict and galvanized U.S. opposition to the war. In response, Johnson announced in March 1968 that he would not seek reelection, citing what he perceived to be his responsibility in creating a perilous national division over Vietnam.

Explanation:

the soviet union wanted to impose communist governments in eastern europe.