We never cut the head off the snake in Afghanistan. That is false. Afghanistan is a series of villages, the elder of each village is the president of said village, they never had a central government and never will. As soon as we walked out of those villages, the Taliban/Al Qaeda would walk in after us and kill anyone that worked with us or refused to shoot at us.
To end it all in Afghanistan, we needed all out war declaration which we didn't do. Afghanistan had open borders on literally every side so terrorist leadership simply fled and came back with more recruits.
That said, I agree with you. You cannot kill an idea and that is what radical Islam is.......it's an idealogy. Also, the world doesn't have the stomach for what would be required to stop it. Better to pull out, boost foreign intelligence, secure our own borders and invest in better weaponry to protect our nation and force NATO to do the same.
The middle east will eat it's own, it always does if you let it.