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.