It's a lesson, if the US Government can learn it.
...What was clear in a few years was that the U.S. military could knock over hostile regimes and rout their regular armed forces. But we could not eradicate a resistance that had time on its side, plus tradition, tribalism, nationalism and an abiding faith that martyrdom and paradise awaited those who died in the cause.
As Napoleon said, “In war, the moral is to the physical as ten to one.”...
Buchanan mentions another lesson, too:
...Hubris was our failing, as it often is of great powers, the mindset exhibited by Secretary of State Madeleine Albright when she declared: “If we have to use force, it is because we are America. We are the indispensable nation. We stand tall. We see further into the future.”
Given Albright's dicta, it's questionable whether the US Government can (or will ever) learn lessons.