There shall be little similarity with either Vietnam or Russia's previous war with Afghanistan.

Both of those were fought under the rules of the Cold War. Both were battles by a superpower which had little public support back home, little support from allies, and with opponents that were being funded and trained by powerful enemies that nobody dared fight directly.

This time the US will go to war with full public support, along with the militaries of most of Europe and quite likely Russia. Any country strongly suspected of aiding and abetting our opponents will themselves become targets of war. That means that more force will be applied, we will be much more willing to take casualties, and whoever is targeted will quickly become isolated from potential support and supplies.

For these reasons and more, I rather suspect a different outcome from the abortive police action that the US undertook in Vietnam...