I think what it gets down to is: A) Is Vietnam as an American War winnable under any strategy. B) What form of US interaction with the situation in Vietnam can achieve the goals of the defeat of the insurgency, alternatively the severe weakening of the insurgency to an issue manageable by the South Vietnamese, and the continuation of South Vietnam as a nation. This is distinct from the Abrams scenario, but is important to understanding what Abrams could achieve. C) The obvious of what would a Vietnam War as managed by Abrams from 1964 look like, compared to the OTL.