Answer:
America “lost” South Vietnam because it was an artificial construct created in the wake of the French loss of Indochina. Because there never was an “organic” nation of South Vietnam, when the U.S. discontinued to invest military assets into that construct, it eventually ceased to exist.
Explanation:
The United States continued to prop up South Vietnamese government with military forces, it is conceivable that the entity could have continued into the 1980s, thus bringing it closer to when the Soviet Union collapsed and most communist nations in the world (China being a notable exception) ceased to exist. However, the American public had grown tired of the loss of American lives and of the war itself, meaning that there’s was no way that U.S. military involvement in the region could continue.
Also, had the United States launched a full-scale military invasion of North Vietnam instead of confining the war to the southern half of the country, the war would have largely ended in the mid- to late 1960s. There would have been some guerrilla actions for years and perhaps some incursions from Laos or Cambodia, but there would have been a unified Vietnam that was noncommunist.
