Partly, leaving Afghanistan is the knee-jerk reaction of an empire in free-fall, ditching a half-assed attempt a colonialism. Vietnam is a legit tourist destination, Afghanistan will never be. Also, our high-rollers are addicted to expensive whisky and cocaine, not opium (maybe opioids, but that's not the people making major political decisions). And, we have legalized cannabis in enough states to saturate the market for high-grade alkaloids (hash is just a fond memory).

Meanwhile, the military/industrial complex has soaked us for a trillion dollars worth of war toys that we just left behind for the Taliban (or Isis) to play war with.

Business as usual... US government IS a total mess!