One of them that's been going around since 1941, the Pearl Harbor disaster was caused by treason in the American government. The government knew the Japanese air raid was coming a failed to warn the Pearl Harbor commanders. Roosevelt's numerous enemies have accused him of conspiring to bring the US into WWII by setting up the Pacific fleet.
I don't buy this. Roosevelt wanted to intervene in WWII and was prevented from doing so by a powerful isolationist movement. But, Roosevelt wanted to use the fleet to do the intervention. The idea that he would sacrifice the fleet he looked to do the intervention, merely to silence domestic political opponents is absurd.
Pearl Harbor happened because US commanders thought Pearl was so far away from Japan as to be immune to Japanese action. They just could not imagine getting hit at Pearl. Even though the Royal Navy had pulled off a very similar air strike on the Italians at Taranto just a few months before.
Pearl even ignored a radar warning. The US Army had a working radar station on Hawaii. It picked up the incoming Japanese strike 180 miles out. The Army radar operators telephoned a warning to fleet headquarters but the junior officer of the day ignored it. If fleet HQ had had it's act together, this was enough warning to scramble aircraft and call for battle stations, get the guns manned and the ammunition broken out of locked storage.
Pacific Fleet also ignored a report from a picket destroyer that had detected, depth charged, and sunk a submarine lurking right off Pearl, in a restricted zone, where no submarines had any business being. To ignore both a submarine warning and a radar warning the same morning takes a remarkable degree of stupidity.