No, technology did not play a decisive role in the outcome of the Vietnam War. If technology had played a decisive role, the United States would have won this war.
In the Vietnam War, the United States had a dominant advantage in technology. For example, the US had almost complete domination of the skies over Vietnam. Its jets and its helicopters gave it mobility that the enemy lacked as well as the ability to provide close air support to its troops. The Vietcong and the North Vietnamese lacked these things and many other technological advantages.
Even so, the US did not win the war. This is because the war was won by the North’s greater motivation and its willingness to undergo suffering in order to win. This was what really played a decisive role in the war. The North Vietnamese were more motivated to win the war than the Americans were. They were more willing to endure hardships than the American populace was. This led to the American public eventually demanding an end to the war because they were no longer convinced that the war was worth what it would cost to win.
Thus, it was motivation and not technology that was decisive in the Vietnam War.
(Before I answer your question, I'd like to just point out my oppositional view about the so called "Vietnam War". I prefer to call it the "Vietnam Conflict" because the United States never really declared war on Vietnam, rather they helped out the South Vietnamese in the War, However, their presence was grand. Anyway, On to your question!!!!)
I say both yes and no. I say "yes" because at that time, the U.S. had a lot of technological advances to warfare then. However, I do say "no" because the U.S. never "won" the Conflict in Vietnam and naver got rid of Communism. With the U.S.'s powerful warfare technology such as jets, Agent Orange, Napalm, the M16, etc. It took 20 years for the U.S. to figure out that this "war" is pointless. Even with all that advanced tech, the U.S. never made a strong hold on the small country. The Viet-Cong and the NVA soldiers had tech supported by and from China and from the Soviet Union. Two strong nations, but they only provided a small military arsenal like rifles, bombs, other equipment; but they used all of it to their advantage.
Also, even with the tech the U.S. had, they forgot one thing that the U.S. should have figured from their own history, they fought on the Vietnamese "Home Land". The U.S. were not used to the subtropic area nor the climate. Plus they came across the planet to fight so you have people with either jet-lag or time lapse with sleep. The Vietnamese were in THEIR land, knew THEIR land very well, and they decided how to use THEIR land to THEIR advantage.
So yes, Advandced tech did make a decisive placement for both the U.S. and Vietnam because both had advanced tech, more for the U.S. though. However, I say NO because even with the technology the U.S. had, there was one thing they didn't have: Knowledge of the land and the ability to counter attack against the over seas invaders.