That is an interesting question.
Well all considered the US government probably implied by giving this cold homecoming to the Vietnam veterans that they had not been courageous and tough enough to win that war : if they had been considered brave enough, the government would have pointed out its own failure, its incapacity to win a war against a technically weak but politically strong country like Vietnam.
In addition the American citizens had failed to support that war and the public opinion had been outraged by atrocities perpetrated in the name of America against civilians and the natural environment (loads of dioxin made by American chemical firms were poured over the tropical forest cover in Vietnam, thus poisoning the soil and the water for future generations and resulting in misformed babies) by defeated troops in a far off country where people had fought against foreign interference (Vietnamese casualties reached a staggering figure of 3 millions during that war even if ot was never officially declared by the US Government).
So the Vietnam veterans not only brought home a bitter sense of defeat, they also gave to the US citizens a bad image of their own country, while the American Nation looked morally bankrupt.
The methods used by the Pentagon to manage B 52s missions over the countryside, performimg massive bombing of civilians and destroying the natural environment were eventually emulated after the war by consultants and sold as new methods of management.
So it seems that dying in Vietnam could not be hailed as a sacrifice to the Nation symbolised nor supported by official discourse, let alone public monuments (unlike after the Pacific war), since it came to be viewed as mere accidents met by anonymous soldiers manipulated as objective statistics, not as heroes anymore.
Thus the Vietnam War opened an new era of technical and unspoken sacrifice that is now implied and accepted by the Globalization process unleashed under the flag of liberalisation, another untold and undeclared war waged against the weaker among human civilisations in the name of a one dimensional modermisation process. The problem this time is that some emerging countries appear to be among the winners and a growing number of casualties is spreading among the middle class right in the center of the western civilisation.