When Pearl Harbor took place, the Japanese did not even dream that in a few years there would be a US four engine bomber (the Superfortress) with a huge range and a flight altitude well out of range of their best fighters, much less that it would drop something as lethal as an atomic bomb on them. Even more than Germany, the Empire saw the airforce as a tactical force supporting their army and navy. The innovation power of a capitalist system and its ability to quickly adapt to wartime requirements within only a few months took them by surprise.
The Japanese never believed they could win the Pacifc War in the sense of conquering America, but they believed that the US was a meek, fumbling democracy that would never pay the blood tribute of an extended war with them. They hoped for a short sharp shock effect, Pearl Harbor and a couple of victorious (for them) sea battles, lots of US POWs on the Pacific islands they took which could be exchanged in an armistice dictated by them with a bruised US, and an isolationist US public led by a President who couldn't even walk right.
It was a shambolic plan, not at all taking a "wake the sleeping giant"-scenario into account. They believed the US would be like Czarist Russia, big mistake. (Just like Hitler underestimated the Soviet Union, thinking they'd be as easy prey as Czarist Russia had been in WW I.) But then Japan had little other choice, their fuel devouring monster of a military machine was on its last drops. They had to do something quickly or give up their Empire building via military force.