Nation building is a very messy, aggressive, expensive and long term commitment. We Americans aren't known for our long term commitments. The Middle East, especially Afghanistan is a case in point.
You can't simply march in to a medieval "country" that's been ruled by tribal factions for 1500+ years and in a matter of a mere decade unite those tribes, suppress an insurgency, install Western institutions and create an enlightened philosophy of civil rights and societal fairness.
Britain was in India for 332 years (starting with the East India Company in 1615). The British were forced out of India in 1947 with India's independence. Shortly thereafter it split on religious lines (Muslim Pakistan/Hindu India). Even after 332 years of forced, often brutal occupation India is still in many ways is the India of pre-British rule.
Our only "success'" in nation building was our 16 years in a defeated, demoralized post-war Japan, and it took 2 nuclear bombs dropped on 2 cities to convince them to accept us on their soil. We've been in Afghanistan for about 10 years as only a military force.
Many have tried in Afghanistan, including Alexander the Great, various Islamic conquerors, Genghis Khan, Britain, Soviets, and now us.
Nation building, especially in less than 2 decades, is a no win scenario, but we never remember that ( i.e. Iraq, Viet Nam, Philippines). It is abundantly true: "Those who cannot remember the past are condemned to repeat it".
We Americans seem to excel in forgetting history!