The most obvious impact on Vietnam was the literal ravaging of the land. The bombing campaigns and ground endeavors helped to destroy so much of the terrain and the land upon which a primarily agricultural society depended. The "Rice Bowl" of the world was significantly altered with the constant presence of conventional and unconventional warfare. The spillover in the later stages of the war to Cambodia had much of the same effect. The Cambodian inclusion in the war revealed much of the brutality and cruelty in the war, as the United States began bombing campaigns in the neighboring nation. Political instability ensued with totalitarian leadership assuming control in Cambodia once the Americans and other Westerners were expelled from Cambodia and once the Treaties had begun to emerge calling for an end to the conflict.
Cambodia fell to communist rebels called the Khmer Rouge in April 1975, at the same time as Laos and South Vietnam did. The Khmer Rouge were a different breed of communist, though. The defeat of government forces allied with the US ushered in a four year reign of terror by the KR and Pol Pot that murdered nearly a third of the entire population. If you spoke a foreign language, you were killed. Had a college degree? Killed. Worked for the old government or the US? Killed. They even shot people who had glasses as they believed it was a sign of education. Then they moved everyone out of the cities to the countryside to form a new farming utopia. So, the result of the Vietnam War on Cambodia was devastating in almost every way.
In South Vietnam and Laos especially, there are millions of mines, bombs and artillery shells that are still unexploded. Massive bomb craters from B-52 raids have now become rice paddies in many places. Approximately 1.5 million Vietnamese were killed on both sides, and nearly 200,000 people fled the country in the five years following the war. Many came to the United States.
Well, of course the Vietnam War was very devastating to the country of Vietnam. Both the North and South were hurt badly. In the North, there was a lot of bombing by American planes. There were also lots and lots of soldiers who were killed in combat. Finally, the people had to make do with very little in the way of food and other necessities during the war.
In the South, the US sprayed Agent Orange to kill plants. This hurt the people economically (killed crops) and it led to major health problems for many people. As in the North, many people were killed by both sides. Many people were moved from their homes and became refugees.
So, as you would expect from a war that went on for years, it really hurt the Vietnamese people a lot.