After the division of Vietnam into North and South the North is seen as a Communist threat by the United States. South Vietnam's Prime Minister, Ngo Dim Diem, faced a 2 year deadline for a nation-wide reunification vote and the US feared that Diem did might not win. Diem's advisers had a dim view of the future as well, believing a Communist victory was inevitable. After the division of the country many Vietnamese Catholics, estimated at 900,000, fled the North. Diem and his brother, who headed the intelligence service, demolished their opponents in the South and created an air of mistrust that would continue far into the future. By the late 1950s Diem relied more and more on his family to help run the country. The Communist forces in the South, the Viet Cong, became a serious threat with rising opposition to Diem. The self immolation of a monk and ongoing protests protests led to a military coup on November 2, 1963 and the death of Diem just a few weeks prior to the assassination of JFK.
—garykmcd