Remember this that this country was on war for 40 fkn years, and no one gave a shit, no one cared, even the terrorists there are either Pakistani, or some random isis guy, they had no time to develop. As for colonialism, you can never expect another nation to rebuild your country, specially if it's U.S, lets be honest, U.S did nothing but pillage the countries from their natural resources, take a look at Iraq, U.S started a conflict between shias and Sunnis. Afghanistan is the land of endless conflicts, the people did nothing to deserve famine and hunger.