How did the attack on Pearl Harbor hurt the US?

In military terms, the Japanese attack on Pearl Harbor did not hurt the United States much at all.  Not that many ships were destroyed and none of the US aircraft carriers were even at Pearl Harbor so the most important ships were not harmed at all.  The US was able to turn around and crush the Japanese at Midway only about six months later.  This shows that the US was not really hurt that badly by the actual Pearl Harbor attack.

The Japanese meant to destroy the entire US fleet by attacking Pearl Harbor.  That would have made it impossible for the US to go out and resist Japan in the Western Pacific.  However, the Japanese failed to actually destroy the fleet.  The aircraft carriers, which would become the most important ships in the fleet, were out of port and so were not damaged.  Only 7 or 8 US ships total were damaged badly enough to be out of service for a year or more.  This is not a very large number.  At the time, it seemed like it was a major loss because it was unexpected and because many people thought that the battleships (which took the brunt of the damages in the attacks) were going to be the most important kind of ship.  As it turned out, battleships were not that important and aircraft carriers became the dominant kind of ship.

So, the Pearl Harbor attack did not really hurt the US in military terms.  Of course, it hurt the families of the people who were killed and it hurt the people who were wounded in the attack.  It ended up hurting Americans of Japanese descent on the West Coast who were interned because Americans feared that they would help bring about further surprise attacks.  But it did not hurt the actual US war effort very much and it certainly helped the US by motivating most people in the country to participate in WWII.