How successful was the American effort to win the "hearts and minds" of the Vietnamese people?
While well intended, and while correctly recognizing the strategic imperative of winning popular support from the South Vietnamese population, the "hearts and minds" program was decidedly ineffective at doing so, at least in any lasting or meaningful way.
The South Vietnamese population, particularly in the Mekong Delta and rural villages, had been numbed by decades of conflict and competing armies occupying their territory, so out of the sheer necessity and pragmatism of day to day survival, they learned quickly to pledge allegiance to whatever flag was offered and whoever had the weapons in their vicinity.
The American effort also recognized that economic aid would be central to winning over anyone, given the poverty and destruction that accompanied the war, but this was nullified by the fact that the Americans did not have the forces to control the countryside at night, and villagers knew the VC would return, sometimes exacting reprisals to those who cooperated with the Americans.
So to sum up, it was a good effort, and necessary in order to have anything like victory there, but the strength of the VC in the countryside prevented the effort from gaining traction and making a real difference.