Even as total as the surprise was at Pearl, the Japanese still took significant losses and would probably have been badly mauled if the US forces had been on alert.
(The responsibility for the naval defense would have fallen to Admiral Kimmel.) (Yes, there should have been a picket line of ships and/or submarines in the waters around Oahu.)
The Japanese losses were a fraction (5%, actually) of the American losses.
It wasn't the losses that ended their attacks, nor was it the American response. They had more time than they themselves knew, so complete was their surprise and so off-guard were the Americans. The unknown was arguably the driving force in the decision to head home after two sorties.
In the end, the Japanese victory at Pearl Harbor may have helped seal their fate at Midway, as Japan left two carriers behind in their belief that four would suffice; had the American response to the attack been more vigorous, it is likely that the Japanese would have taken us far more seriously six months later and put all six carriers to sea for a second voyage across the Pacific.
Look at all the long range float planes sitting on the ground rather than fanned out hundreds of miles from Pearl on patrol.
The Japanese losses were a fraction (5%, actually) of the American losses.
Japanese aircraft losses were 29 or about 8.5 percent of the strike force.
At that rate, all attacking Japanese aircraft would be lost in 11 such attacks.