Why was the USA so unprepared for the attack on Pearl Harbor in 1941?

Transcript
Clip from British newsreel called Pearl Harbour – First Pictures, January 1942

Catalogue ref: BP190242131817
Courtesy of ITN/Source

The December disaster at Pearl Harbour; this is how the great American naval base looked after waves of Japanese bombers had carried out their stab in the back raid.

The Battleship Arizona and four other warships destroyed. The Airbase on the island and large numbers of aircraft bombed and burned out in one devastating treacherous blow. Japan’s vicious attempt to cripple the American Pacific fleet before any declaration of war.

Taken by surprise the fighter aircraft at Hickham Field and Wheeler Field had little chance of engaging the enemy bombers who were thus able to wreak their destruction almost unhampered.