I have had two brushes with Vietnam during my life: one was serving in the Army artillery in Vietnam during the war, the second was overseeing databases of Vietnamese who wanted to go to the United States after the war.
When I was in Vietnam from 1969 to 1970, I had very little interaction with the Vietnamese. I was in a heavy artillery battery that supported American Army soldiers on the ground. Most of the time we were stationed at firebases in the middle of nowhere, with no Vietnamese around. A few times we had Vietnamese units on the same firebase, but we did not interact. They supported Vietnamese units and we supported American units. We were in northern South Vietnam, which the Army called I Corps. Occasionally I would ride into town with supply trucks; so, I occasionally saw Hue and Quang Tri. At Firebase Barbara, on a lonely mountaintop not too far south of Khe Sanh on the Laotian border, all of our resupply was done by helicopter. When Saigon fell, I had no personal connection to any South Vietnamese left behind.
At the American Embassy in Bangkok, Thailand, from 1984 to 1986, I was in charge of the embassy’s computers. I was primarily responsible for the computers in the embassy, which mainly handled administrative tasks like maintaining personnel and financial records. However, as the senior computer person in the embassy, I had oversight responsibility for several other computer operations. One of them handled data for the Orderly Departure Program for Vietnamese still in Vietnam who wanted to leave the country. The Orderly Departure Program had been established to try to stop the dangerous exodus of Vietnamese “boat people.” Another handled data for Vietnamese refugees who had already escaped across Laos or Cambodia to Thai refugee camps and who wanted to go to the United States. This was about ten years after the fall of Saigon, but I don’t know how many of these people had worked for the US during the war.
According to Wikipedia, from 1980 to 1997, 623,509 Vietnamese were resettled abroad under the Orderly Departure Program, of whom 458,367 went to the United States. As I recall, a friend at the embassy in Bangkok who worked in the Orderly Departure Program went to Vietnam about once a week to process a planeload of Vietnamese going to the US. Outside of the Orderly Departure Program, the number of “boat people” leaving Vietnam and arriving safely in another country totaled almost 800,000 between 1975 and 1995. The UN High Commissioner for Refugees estimated that between 200,000 and 400,000 boat people died at sea without reaching their destination. About 40,000 Vietnamese refugees were held in Thai border refugee camps until they could be resettled.
If Vietnam is an example, there will continue to be many refugees fleeing Afghanistan for years to come.