There was a civil war before 2001, and there would almost certainly be another if ISAF withdrew. Once the existing Government fell (probably not long) it would no longer be an insurgency, as an insurgency requires a government.
I don't see how ISAF vs Taliban can be called civil war, since ISAF is an external force pursuing its own objectives.
I'm not sure how useful a distinction between terrorism and insurgency is. Terrorism is a tactic; it can be used by an insurgent, by a counter-insurgent, or in pursuit of inter-state objectives that have nothing to do with insurgency.
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