It is if you look at a map and conclude the terrain is flat. It is a nightmare for any military. This is a funny chortle, I geddit, but if we're to take this at face value:
Alexander the Great's army was garbage. He managed barely by marrying a local noblewoman after a long and frustrating campaign. He had the benefit of not being on the opposite side of the planet. America had to fly over Iran to get there. Super easy.
The British were garbage. The first Anglo-Afghan war went .... poorly. They had the same experience as the US forces. The second Anglo-Afghan war went great! They defeated the Afghan army! A few months later they lost Kabul, their forces collapsed immediately, being slaughtered again by Afghanis. They reinvaded, failed, and retreated. They would have totally won if they had an air force.
The Soviet military was garbage. They struggled for a decade to prop up their own government there. (Sound familiar yet?)
There was a third Anglo-Afghan war. This time the British won handily. Just kidding, they failed yet again, like everyone else.
This is like me telling you: "If you're so smart, why aren't you a billionaire?" Well, that isn't how it works, is it?
Afghanistan is extremely difficult to control and has been for thousands of years.