Freedman notably warns to avoid those who proclaim, "the ease and speed with which victory can be achieved while underestimating the resourcefulness of adversaries."
Unless the US military does not believe in the saying "Never Underestimate You Enemy". Anymore ?
But the US did forget about max effort to end the war quickly to save "blood & treasure" etc. Well … maybe the military didn't but the elected officials did. And didn't listen to their military advisers, etc. at times.
The things we see today with insurgencies/terrorism being the norm so often. As major 1st World Powers know. A big war between East & West would really be in no ones favor in the long or even short run.
And I'm not even thinking about deploying nucs. Just conventional war. But the outcome would be the same. No one wins either way.
The weaker nations' insurgencies and terrorism is their best if not their only weapon to take on the 1st World major forces. As with all insurgencies the guerilla/insurgent/partisan and even terrorist blend in with the locals as in many cases they are not only supported by the locals. But many are the locals. With the only distinction is with the advent of "Foreign Fighters" flocking to the jihad, etc. To supplement the local. And uniforms are generally not wore.
Plus some 1st World nations support the insurgents with weapons, money, etc. And they have the "home court" advantage like all insurgencies as well. The new paradigm for wars seems to be strongly leaning towards insurgencies. As in many cases the insurgent/jihadi, etc., believes he has nothing to lose. Especially if they believe as many do. If they die fighting the "infidel", non-believer, etc. they are assured a better "afterlife"(?).
However it's not rare that pundits and futurists, etc., have been wrong. As many predictions are based on biases and at times subconscious "wishful thinking". Like all of us on occasion. But only time will tell … as always … and on the other hand hindsight is generally always 20/20 …