Massoud fought against an occupying attacker (SU) before getting involved in the civil war. At the time he was killey by Al Quaida he was rather isolated as the Taliban hat alread conquered most of Afghanistan including Kabul. Eventhough he warned the West against Binladen (which was most probably his death sentence) I don’t think him being alive would have made a difference as the US was, again, a foreign occupier. Since Massoud was nearly defeated I find it improbable that he could’ve defeated the Taliban and the US… or that him being an US ally (as he was before against the Soviets) would have increased rhe acceptance of the US invasion.