Lots of interesting points brought up.
Japan had ambitions and somewhat resented the Washington Naval treaty which limited ships to a 5:5:3 ratio between Britian, US and Japan. Without that treaty though it would have bankrupted nations who were planning on a naval arms race. Remember the biggest navel battle in history was at Jutland in WWI.
The Japanese knew that they'd have no chance of defeating the US in a regular war. Yamamoto knew that as he had studied in the US and knew US industry was much larger than Japan. The only chance he felt they had was to knock out the US fleet at Pearl and hope that with their fleet out of action that the US would sue for peace. That sorta backfired as they didn't anticipate the US response. Some would say that they were somewhat forced into it as the US was a major oil exporter at the time and the US had cut off oil to Japan due to their invasion of Manchuria. So Japan either had to withdraw or go to war with the US and secure it's own oil supplies in the west indies. There were long on going negotiations that lasted months before December 7. The US actually were somewhat prepared for an attack the Sunday before. They had long range catalina flying boats which were used for recon, but it's all visual, if weather was bad, they wouldn't be seen. Probably part of the mindset at the time that if they were going to attack, it'd be somewhere closer to Japan and that their fleet wouldn't make the long journey to Pearl.
The US does make a big deal about the surprise attack, but that's somewhat traditional in war. Hitler never really declared war on any of the countries he invaded, except the US and that proved to be a mistake.