Which event is often referred to as Japan's infamous surprise attack on the U.S.?

The event often referred to as Japan's infamous surprise attack on the U.S. is the Attack on Pearl Harbor. This military strike took place on December 7, 1941, when the Imperial Japanese Navy conducted a surprise aerial attack on the U.S. naval base at Pearl Harbor in Hawaii. The objective of the attack was to disable the United States Pacific Fleet, which Japan viewed as a significant obstacle to its plans for expansion in Southeast Asia and the Pacific.

The attack resulted in significant loss of life and damage to the U.S. fleet, including the sinking or damaging of eight battleships and numerous other vessels, as well as destruction of aircraft. The event shocked the American public and led to the United States' formal entry into World War II the following day when Congress declared war on Japan.

In contrast, the other events listed are major military confrontations but do not hold the same context of a surprise attack aimed at bringing the U.S. directly into the war. The Battle of Iwo Jima and the Fall of Singapore were important battles later in the war, and the Battle of the Coral Sea was a significant naval engagement, but none of them match the specific nature and implications of the attack on Pearl Harbor.