Final answer:
The U.S. war in Afghanistan (2001–2021) can be described as interventionism, a foreign policy approach where a country actively involves itself in the affairs of other nations.
Step-by-step explanation:
The U.S. war in Afghanistan (2001–2021) can be described as interventionism. Interventionism is a foreign policy approach where a country actively involves itself in the affairs of other nations. The U.S. intervened in Afghanistan to combat terrorism after the 9/11 attacks and to support the establishment of a stable government.