Answer:
Cognitive dissonance
Explanation:
In the field of psychology, cognitive dissonance occurs when a
person holds two or more contradictory beliefs, ideas, or values, or
participates in an action that goes against one of these three, and
experiences psychological stress because of that. According to this
theory, when two actions or ideas are not psychologically consistent
with each other, people do all in their power to change them until
they become consistent. The discomfort is triggered by the
person's belief clashing with new information perceived, wherein
they try to find a way to resolve the contradiction to reduce their
discomfort.
From the above, you'd realize that the American's were suffering from cognitive dissonance because prior to the Iraq war only 38% of Americans said the war was justified even if Iraq did not have weapons of mass destruction.
When no such weapons were found after the war, 58% of Americans then supported the war.(Here, new information surfaces,it clashes with their previous beliefs and their views changes)