"Haunting Vietnam," by Marvin Kalb and daughter.

Have not read the book, but watched the two authors answer questions about it on C-Span on 8/7/11.  Their premise: all foreign policy and attitudes are influenced by the quagmire the US found itself in in the Vietnam conflict.  Marvin Kalb made a very heartfelt comment that the soldiers, airmen, and sailors did not lose the war - the United States lost the war.  In other words, the troops fought bravely, but the decision was made politically that it was not worth losing more Americans to  continue.