JFK was a foreign policy disaster, and to take off the pressure, he got us into Vietnam, he was a boob.
No JFK, no Vietnam war, and no 1965 Immigration Act, and no unionized government, and Castro would not still be there 50 years after him.
Sure, any president since Kennedy, or before Kennedy, (in the case of Korea) to include Kennedy, could have just ignored Vietnam, much as presidents before them did. But they were swayed by fearful political arguments first in Korea and then in Vietnam that Communism was expanding, as I indicated.
But nobody ignored it except for Truman and he could. Under Eisenhower it became a UN problem and thus we got involved to save the free world. It all made so much sense then...
The U.S. government viewed American involvement in the war as a way to prevent a Communist takeover of South Vietnam. This was part of a wider containment strategy, with the stated aim of stopping the spread of communism. According to the U.S. domino theory, if one state went Communist, other states in the region would follow, and U.S. policy thus held that accommodation to the spread of Communist rule across all of Vietnam was unacceptable.
Beginning in 1950, American military advisors arrived in what was then French Indochina. U.S. involvement escalated in the early 1960s, with troop levels tripling in 1961 and again in 1962.[39] U.S. involvement escalated further following the 1964 Gulf of Tonkin incident, in which a U.S. destroyer clashed with North Vietnamese fast attack craft, which was followed by the Gulf of Tonkin Resolution, which gave the U.S. president authorization to increase U.S. military presence. Regular U.S. combat units were deployed beginning in 1965