Japan imported oil from the US in the 1930's, oil which they used to drive their growing war machine. This meant that US oil exported to Japan was being used to fuel their war efforts; they had, since the late 1890's, invaded and fought wars with pretty much everyone around them including Russia and China.
Interesting summation of the events leading to Dec 7 1941:
http://www.bbc.co.uk/history/worldwars/wwtwo/japan_quest_empire_01.shtml
The US had its own problems dealing with the Depression etc and since WW I was still pretty fresh in people's minds there was a strong isolationist movement in this country. So a lot of people in government took the view 'if we don't mess with them, they won't mess with us'. For that reason, US policy was pretty much 'hands off' even during the Japan-China war, which started in 1937. The Japanese delegation to the League of Nations walked out in 1933 over what they perceived as Western meddling in their affairs, thus showing they had no intention of working things out.
In July 1941, Japan invaded various Pacific Rim countries including Vietnam and Korea and were still fighting a war in China. In response the US government cut off oil exports to Japan. Instead of seeking oil elsewhere, the Japanese military decided the best plan was to attack Pearl Harbor, maybe to force the US to export oil to Japan again. In retrospect, not the best policy.
So the whole 'the US oil embargo of Japan was solely responsible for Pearl Harbor' argument leaves out the backstory and the Japanese government's growing aggression.
The delayed translation story is a red herring, it didn't matter whether war was declared an hour before or an hour after the attack, the fact remains that Japan intended a hopefully crippling surprise attack against the US Pacific Fleet.
Admiral Yamamoto said later 'I fear we have awakened a sleeping giant'. How right he was; when the first bomb hit in Pearl Harbor that was the end of US isolationism. Germany had signed pacts with Japan (thus creating the 'Axis' powers) and declared war on the US shortly afterward, so far from being a victim of US imperialism instead Japan started that little E36 M3storm trying to expand their territory and being in a constant state of war.
Trivia: as a 'reward' for being on the side of the Allies in WW I, Japan was given Germany's colonies in the Pacific.