on various problems faced in Vietnam among US forces as mentioned by PB (e.g., "racism, social problems, refusal to obey orders, killing of officers etc."). Were those problems peculiar to the military, or were they a reflection of the changes in American society during the 60s and 70s ?

As time went by in Vietnam, the American forces transitioned from a purely professional force (e.g., the early advisors) to a majority conscripted force. IIRC, the overall (for all the war) enlistee-draftee ratio was ~ 2/3 to 1/3. As the force became more conscripted, one would expect it to more reflect American society as a whole, and to reflect the problems in that society as it moved through the 60s and into the 70s.

Regards

Mike