Well for example government policy could be for the Japanese to attack Pearl Harbour to provide a pretext for America to enter WWII against Germany, but as you say there wasn’t an official vote in Congress asking them to attack.
However the American oil embargo imposed on Japan with an ultimatum to leave Manchuria would raise the prospect of this happening, but the Pearl Harbour commanders weren’t informed of the worsening diplomatic situation.
If they had been they could have prepared defensively, but this would have forestalled the Japanese attack which was a dependent on surprise. Roosevelt declared a day of infamy, for which he was responsible, by omission.
The evidence became the cover-up as the commanders weren’t court martialled to avoid the truth being told, but job done, as America marched into war.