South Korea is kind of an exception. They are still technically at war with the North, and the U.S. has signed a pact to continue to defend them.
We've "left" Iraq...but the Embassy is a Fortress. "The Embassy of the United States in Baghdad is the largest and most expensive of any embassy in the world. At 0.44 square kilometers it is nearly as large as Vatican City." Anyone who thinks that we are not still directly involved in Iraq's affairs needs only to look at that beast. Anyone who doesn't think the US uses that "embassy" as a base for clandestine operations is a fool.
Afghanistan is a problem. It has always been a problem (for the Russians prior to the US) and it will always be a problem. A lot of that is the simple constant flux due to the demographics of Afganistan. Too many diverse tribes. At least there, the United States has a large amount of coalition support. Furthermore, India will be taking over, similar to the alliance that the US has with South Korea. Though it's pretty obvious what India's motives are, considering the particular country they can now pincer between Afghanistan and India (for those not up to date on geography or history, it is Pakistan, who are no friends to India).
We live in interesting times. Isolationism simply will not be possible.