"I use "invasion" as a neutral term to mean what happens when a foreign army moves in and sets out to displace the existing regime."

Ah so Pakistan did "invade" Afghanistan, whereas the USA who were assisting the internatioanlly recognised Government of Afghanistan were not.

Remember that from 1989 to 1992 a "Civil War" raged in Afghanistan but in 1992 a Government was formed from ex-Mujahideen Warlords and the UN recognised it. In 1994 backed by the Pakistani Government, Army and ISI the Taleban reignited the "Civil War" which was still ongoing at the time of the 9/11 attacks. The USA agreed to provide assistance to the internationally recognised Afghan Government and a fellow member of the UN. In short Kevin there was NO U.S. INVASION