The Democrat Party secured defeat. Responding to Tet, those that got us into war cut and ran. In 1972 a Democratic Congress refused funding to restore South Vietnamese forces, which had defeated the invading NVA army. Soviet and Chinese support brought NVA victory in 1975.
A few examples from the History Channel show the disinformation campaign waged against Vietnam Veterans. U.S. forces took extraordinary steps to avoid civilian deaths, while the VC and NVA murdered over 36,000 by targeting village leaders, teachers, and medical workers. Two-thirds of Vietnam vets volunteered compared to only one-third of those in WW II. Over 90% of Vietnam Veterans say they are glad they served and 74% would serve again knowing the outcome. Compared to non-veterans, they were more likely to find employment and then earned 18% more.
Ronald Reagan said of them, “ours (mine) was a noble cause. A small country (including ethnic Chinese, Catholic Vietnamese, and others fleeing Communism) newly free from colonial rule sought our help in establishing self-rule and the means of self-defense against a totalitarian neighbor (Tonkinese) bent on conquest.” He said to consider otherwise dishonored the memory of over 58,000 who died in the cause.
War should be regarded as a continuum, and not a dichotomy between violence and diplomacy. Mao Zedong distilled a chapter of Sun Tzu when writing in his red book, “It can therefore be said that politics is war without bloodshed while war is politics with bloodshed”. For eight years we shed our blood in Vietnam and then politicians managed to develop strategies to secure defeat.
Dereliction of Duty: Johnson, McNamara, the Joint Chiefs of Staff, and the Lies That Led to Vietnam by H. R. McMaster
The Day It Became the Longest War
https://www.usni.org/magazines/proceedings/1996/may/day-it-became-longest-war
Statistics about the Vietnam War
http://vhfcn.org/stat.html
Not to put too fine a point on it, but ARVN troops were no match for the NVA.