I feel the need to chime in here so please forgive me.
You forget that the North Vietnamese were ideologically committed individuals who were ready and willing to implement Vietnamese independence at all costs after years of occupation. The Vietnam war started out as such but eventually morphed into the position of Vietnamisation, hoping that the South Vietnamese would be able to stand up against the National Liberation Front for South Vietnam (Viet Cong) and PAVN incursions form the North and West. The Viet Cong started out a multiparty organisation with the aim of driving out all "oppressors" but with attrition and Hanoi's influence, the multiparty individuals that were left became marginalised thereby ensuring Hanoi's complete control over the Viet Cong.
We have not even covered the Republic of Vietnam Army (ARVN) which man for man eventually completely dominated (18th ARVN Division and Rangers for example) the Viet Cong and PAVN in the field. The key issues can directly be traced back to a corrupted Government/Officer Corps at a division level and above (the biggest issues) combined with the elimination of aid by Ford Administration. People forget the ARVN was the 5th largest and most experienced Army in the world when it came to Counter Insurgency (COIN) operations.
The politics of South Vietnam are an interesting case study because the constant fear by the various governments of coups never allowed them to fully concentrate the best of their divisions in the field against the Viet Cong/PAVN. We struggled to "Win their Hearts and Mind" but whatever progress we made would quickly become undone by the South Vietnamese government in some act against the civilian populace (see the oppression of Buddhism as a prime example) and the "Strategic Hamlet" program.
Now you mention technology which begs me to ask you how long did Osama bin Laden maintain his position without compromising it for so long? People... Again we circle back to those who are ideologically committed to the "cause" and no amount of force or pressure can ever dissuade them or replace their beliefs. The threat of "oppression" can make people do what is necessary to survive no regardless of the cost.
Let us not forget the immortal words of Ho Chi Minh "You can kill ten of our men for every one we kill of yours. But even at those odds, you will lose and we will win. "