But certainly, half the idea was to force military actions that would divide political support here, then play them up to the useful idiot crowd. That part you can indeed say "worked". Then again, it didn't exactly elect George McGovern. Notice also that it was hardly our domestic useful idiots who had lost their security. In Algeria, the last to give up were the Harkis, and in South Vietnam, the last to give up were the ARVN.
Moral - let's not call too loud on "inevitability" to cloak our own failings.
Keep in mind that in Viet Nam by 68-69 we were wiping out the VC cadres and infrastructure in the South using the Phoenix program. This was JasonC's "well aimed" counter terrorism done very well. Between the Phoenix Program and the losses in Tet 68 the VC were on their backs: those losses had to be made up by sending vastly more NVA down the HCM Trail.
This movement of NVA was not interdicted for political not military reasons. Even after US main battle force departure and Vietnamization the war was at best a stalemate, and the North finally won with a conventional invasion only after the US Congress cut off military assistance to the RVN in 73-74, largely as a swipe at Nixon post Watergate.
In terms of Algeria, El Salvador and other cases where there is no HCM Trail and no NVA to send into the war, it is possible to wipe out the terrorist leadership and cadres with tightly focused well aimed "Phoenix Program" type operations without blowing up so many civilians that they are alienated and driven into the terrorist camp. We were doing it well in the RVN, and we did it in El Salvador, a clear victory for our side. We will have to do it on a large scale now in Afghanistan.
The unreported war will be the critical part of it, the "Phoenix" war.