What pivotal event led the United States to enter World War II?

The event that led the United States to enter World War II was the attack on Pearl Harbor.

The attack on Pearl Harbor was a surprise military offensive by the Imperial Japanese Navy against the United States naval base in Pearl Harbor, Hawaii on the morning of Sunday, December 7, 1941. The attack was intended as a preventive action aimed at to avoid the intervention of the United States Pacific Fleet in the military actions that the Empire of Japan was planning to carry out in Southeast Asia against the overseas possessions of the United Kingdom, France, the Netherlands and the United States. The Japanese made this offensive coincide with the attack on the possessions of the British Empire in Hong Kong, Malaysia and Singapore, which were already in their possession in mid-February 1942.

The attack began at 7:48 AM, local time, and was carried out by 353 Japanese aircraft that included combat fighters, bombers and torpedo boats that took off from six aircraft carriers. The eight American battleships moored in the port were damaged, and four of them sank. Of these eight, two were refloated and four repaired, so that six could return to service later, during the war. The Japanese attack also sank or damaged three cruisers, three destroyers, a school ship and a miner. The Americans lost 188 aircraft, 2403 Americans died, and 1178 others were wounded in varying degrees, but the Japanese did not attack the power station, the shipyard, the maintenance facilities, the fuel tanks and torpedoes, the submarine docks, and the building of the headquarters and the intelligence section. The Japanese lost 29 aircraft and five mini-submarines, in addition to suffering 65 military casualties among the dead and wounded. Likewise, a Japanese sailor was captured alive.

The attack deeply shocked the American people and led directly to the entry of the United States into World War II, both in theaters of war in Europe and the Pacific. The day after this offensive, December 8, the United States declared war on the Empire of Japan.The internal support in North America for the non-intervention in the world conflict, which had been strong, disappeared. Nazi Germany and Fascist Italy declared war on the United States on December 11, in response to operations launched against the Asian power of the Axis.

The bombing of Pearl Harbor by the Japanese military was the pivotal event that led the US to enter World War II.

On December 7, 1941, the US naval base in Hawaii was attacked by the Japanese. This attack resulted in the deaths of over 2,000 American citizens and military personnel. The day after this attack, President Franklin D. Roosevelt gave his famous address to Congress, asking them to declare war on Japan. The US officially entered World War II on December 8, 1941.