How did the Japanese miscalculate the U.S. response to the attack on Pearl Harbor?

Answer 1

The Imperial Japanese Army was on par with most of the world's armies in 1941, but not the most powerful of them. The Imperial Japanese Navy, on the other hand, was the most powerful navy in 1941; so it is an ironic twist of fate, that the weaker Imperial Army influenced Japan more than their navy did. For the most part, the Imperial Navy KNEW what they were doing, and pretty well KNEW what the outcome would be, the army was more optomistic and overly aggressive, and ultimately won out, on the issue of attacking the US. Once the order had been issued, the navy put to sea and commenced battle. To add further salt to the wound, the Japanese army, who had pushed for war with the US, fought well in the South Pacific, but lost many of their battles. The Japanese navy, on the other hand, who gave arguments against war with the US, produced some spectacular victories, such as the "Battle of the Java Sea", "Battle of Savo Island", to name a few.
The Japenese intended to cripple the American Navy with the attack on Pearl Harbor. Instead they only destroyed a few warships and brought the U.S. into the battle. Once the Americans joined in the war, the Axis powers quickly began losing.

Answer 2

They thought that it would make the population of the United States feel defeated. In reality it did the opposite. Just like 9-11 people got mad and were ready to fight.