Most people didn't support the war, so you can sing in the POV of an American hippie, soldier, Vietnamese soldier, citizen, or government official. According to many websites, folk music started the spark of protest against the war. This means that maybe you can sing in a folk song theme. The war was long and brutal, which is why I would not support the war. You could divide it into 5 stanzas with 4 lines each.
One stanza could be:
Life in Vietnam is hard for me,
When I wake up I hear M16's,
When the bombs rain down I know things are changing,
This skirmish is rapidly raging,
Hope it's not cringe :)
