Final answer:
The United States became more deeply involved in Vietnam after the Geneva Accords in 1954 through the assassination of President Kennedy. Kennedy's successor, Lyndon Johnson, chose to escalate US military involvement in Vietnam by sending more troops and engaging in a full-scale war against the Communists in North Vietnam.
Step-by-step explanation:
After the Geneva Accords in 1954, the United States became more deeply involved in Vietnam due to the assassination of President John F. Kennedy. Kennedy had been supplying money and military advisors to bolster the South Vietnamese government, but his assassination led to a change in strategy for his successor, President Lyndon Johnson. Johnson chose to escalate US military involvement in Vietnam, sending more troops and engaging in a full-scale war against the Communists in North Vietnam.