Was Japan successful in their attack of Pearl Harbour?

That depends on what you define as "successful". If we take their aim of the attack, which was not to raise the flag of the Rising Sun over the White House or even Honolulu, but to cripple the USAs' fighting strength in the Pacific until the Japanese could secure the resources in Southeast Asian colonies, thus forcing the US to fight a decisive battle hundreds of kilometers from the Home Islands, then yes, it was a success. u/jschooltiger goes into much more depth about the hopes of Japanese planners with Pearl Harbour here, so I recommend reading that first before we get into the actual "success" of the whole plan. This response will focus on the "material" losses with a small conclusion on the greater strategic picture. With that out of the way, let's begin.

The US Navy

On paper and at first glance, the American Pacific fleet was definitely hit hard by the Imperial Japanese Navy (IJN) on December 7th, 1941. 2,403 servicemen were killed as a result of the attack, and approximately 339 aircraft scattered at airbases around Pearl Harbour were destroyed (most on the ground, though a rare few did manage to make it up into the air before being torn apart by experienced Japanese fighter pilots). An estimated 21 ships of various size and designation were sunk or severely at Pearl, about 20% of the 101 ships docked at harbour that day.

Now a lot of "pop-history" coverage focuses on the Battleships which were damaged or sunk at Pearl, about eight in total (Arizona, Tennessee, Nevada, West Virginia, Maryland, Oklahoma, California, and Pennsylvania). But these losses are actually rather insignificant for two key reasons: firstly only two Battleships were actually lost, in the sense that they were beyond repair and properly out of commission. These were the Arizona (which remains a memorial to the attack this day) and the Oklahoma (which had rolled over on its side but was still salvaged for scrap metal. Perhaps even more conveniently however, both these ships were actually due to be withdrawn shortly after Pearl. They were the two of the oldest vessels (Arizona laid down in 1913 and Oklahoma launched in 1914) of the fleet and were due to be declared over-age in 1942 (basically meaning their duties as combat ships would be heavily reduced). By nature of the shallow water depth at Pearl Harbour, which was only 12 meters (40 feet) at the deepest point and in some areas even as low as 9 meters (30 feet), the damaged battleships just sat slightly lower in the water than they usually did.

Somewhat interestingly, the Japanese may have actually done a favour by sinking the USS Utah, which by 1941 was a target ship meant to be used for practice by American aircraft. In essence by taking this ship out, the Japanese aviators had just managed to do what the American pilots had not yet managed to do.

So out of the actual 21 ships supposedly "damaged or sunk" at Pearl Harbour, the actual number dwindles down to two very old battleships and one target ship. All of the battleships, destroyers, and remaining vessels the Japanese had targeted on December 7th would take part in Pacific battles which contributed to the surrender of Japan in 1945. The perfect example of this was the crippling Battle of Leyte Gulf in 1944, where five of the six American battleships present had been damaged at Pearl Harbour just 3 years prior.

More importantly however, none of the three aircraft carriers operating with the Pacific Fleet had been present at Pearl Harbour on the day of the attack, and it was the absence of these units which Adm. Isoroku Yamamoto is believed to have been concerned about. USS Enterprise was just returning from a routine aircraft delivery to Wake Island, Lexington was on a similar mission to Midway, and Saratoga was in San Diego harbour collecting aircraft and crew after a major refit.

Historian H.P Willmott goes even further (perhaps slightly too far) in illustrating just how immaterial the losses had been at Pearl Harbour for the USN:

"Such was the scale of American industrial power that if during the Pearl Harbor attack the Imperial Navy had been able to sink every major unit of the entire U.S Navy and then complete its own construction program without losing a single unit, by mid-1944 it would still not have been to put to sea a fleet equal to the one the **Americans could have assembled in the intervening thirty months."**^(1)

The Aircraft and Absentees

Of the 151 planes the Japanese damaged and the 188 which were either destroyed or cannibalized for spare parts, the Americans were able to salvage a fair bit of them. Keep in mind that almost one-third of the Army planes however, were already obsolescent and due to be decommissioned in a few months. 80% of the 120 damaged Army planes were able to be repaired, supplemented by planes which had been decommissioned on December 7th but put into operation. In less than two weeks the Army had almost as many planes in operation as they did before December 7th, an impressive recovery.

Alongside the negligible targets which the Japanese did manage to hit in Pearl Harbour, there were the important targets they did not hit at all. Half of the light cruisers, 86% of the destroyers, and all of the heavy cruisers suffered no damage during the attack. The shore facilities at Pearl, which assisted massively in the salvage and rescue efforts in the days following the attack, were also left unscathed. Perhaps the "bullseye" (alongside the three missing carriers) which the Japanese also failed to target were the oil storage facilities near Pearl, which had been filled to full capacity beforehand. Had these storage areas been hit, its likely that the Harbour would have suffered from further damage and thus further delay American combat operations.

Strategic Significance

What the Japanese attack on Pearl Harbour did manage to do was ensure that no American reinforcements from Hawaii could sail to aid the Philippines, Wake Island, Singapore, or any other Southeast Asian colonies which were soon taken over by the Japanese. The Americans had been caught off guard for sure at Pearl Harbour, but one of the possible reasons why is that the Navy and Army command found it hard to justify such an attack by the Japanese (though of course, other diplomatic and intelligence blunders plagued the day).

By crippling the US's already limited ability to respond to Japanese offensives in what would later become the "Southern Resource Area" (encompassing the Southeast Asia colonies of British Malaya, Singapore, the Dutch East Indies, and to an extent the Philippines), Pearl Harbour did succeed in carrying out the aims of the war planners back in Tokyo. They expected a decisive showdown with the Americans which might cause them to sue for peace, and by negating the "threat" posed by the Pacific Fleet at Pearl, that showdown was delayed until the Japanese Navy and Army had acquired the necessary resources to retain fighting strength for a prolonged conflict.

Regardless of whether the Japanese attacked Pearl Harbour or not, historians often argue that the Pacific war would still have taken the four years that it eventually did. Two years for the Americans to make good on the Japanese advantage in aircraft carriers, battleships, destroyers, and other vessels, and two years of actual fighting to advance towards the Japanese mainland. All this alongside the war in Europe following Nazi Germany's declaration of war against the US four days later.

To end this response, I'll leave a quote here from John Mueller on the matter:

"[M]ilitarily, the damage inflicted was more of an inconvenience than a disaster."^(2)

Hope you found the information on here helpful, and feel free to ask followups on why Pearl Harbour was (and to an extent still is) perceived in mainstream historical media as a "disaster".