There were several different effects of the US participation in the Vietnam War during the 1960s. This includes:
1) Increased protests: Many American citizens were displeased with the US increasing their involvement in the Vietnam War. Citizens felt that the US was sending millions of American citizens to fight/die for a cause that many Americans did not support.
2) Increased amount of soldiers sent overseas: During Lyndon B. Johnson's presidency, specifically 1966, he called for an increase in the amount of US soldiers in Vietnam. Overall, millions of men served in the Vietnam War and died fighting to prevent the spread of communism. This greatly affected the US population.