How has the u.s foreign policy led to the chaos in Afghanistan

Are you asking for an opinion here, or are you asking from the standpoint of the novel.

Standpoint of the novel

The 2001 terrorist attacks on the United States initiated the onset of President George Bush's “War on Terror.” I don't know about his policy leading to chaos in Afghanistan per se, but the toppling of the Taliban led to the improvement of conditions in Kabul.