Afghanistan is drowning in guns - I don't see a liberal democracy emerging there anytime this century (please let this be my "Dropbox is a weekend project" comment - I'd love to be wrong.)
Afghanistan is different from Iran. Even today, Iranians are highly educated and they have historically been highly educated. Most of Afghanistan that the US was trying to mobilized was uneducated and living in tiny villages with no real stake as to who won or lost. With Iran's highly educated population and militarized, they have a much better chance of standing up to the fascist government and enacting change.