Japan had been warred with China for 4 years before it attacked U.S.A
Japan had good military technology but it lack of resource.Japan wanted to take over China as China was weak at that time but had plenty of resource. Japanese people intended to defeat China within 3 month.However,Out of their expectation, they have been warred with China for 4 years but still could not conquer it.Then, Japan suddenly attacked the Pearl Habour.
One of the reason why Japan loss may be their military power is not well equipeed in some way. Besides, many of its resource and military power had already been depleted when it warred with China.
Japan's equipment was pretty much as good as anyone's at the beginning of the war, but, as you say, they did not have the resources or infrastructure to make continuous improvements. The Zero was a good plane at the beginning of the war (even with the lack of armor)- they certainly crushed the American Buffalo- but at the end of the war no major changes had been made to it, whereas the Americans were able to make their planes better and better.
The "banzai charges" were of course a really stupid tactic that often crippled their defenses. Only a few commanders were willing to set aside the suicidal ethos in favor of sound military tactics.
I read somewhere that their standard issue infantry rifle was poor quality.
My understanding (remembering conversations with Japanese military geeks) is that the rifle was okay. But bolt-action rifles versus semi-automatic M1 Garands was just not going to be a fair fight, as the Germans found out too.
There were Japanese sidearms that were indeed poorly made- as the war went sour for them this had as much to do with shoddy materials and manufacturing as with inherent design flaws.
The materials and manufacturing is the important point here. When it gets down to it, a bolt action is a bolt action. The older 6.5mm Arisakas I have heard are really good guns. Depending on my financial situation in the near future I may be able to comment better after having one, but for now, I haven't heard anything bad about them. The 7.7mm ones degraded. Mostly because they were newer and many of the ones built at the end of the war were done in people's living rooms.
Where they were inferior was in submachineguns and machineguns. The Type 96 and 99 seem to have been at least as good as the British Bren guns and the Russian DP. It was probably superior to the American BAR as it was an actual machinegun rather than an automatic rifle. It was likely inferior to the US M1919 and German MG34/42. The Type 11 was an antiquated turd. As for submachineguns, the Japanese didn't really have a gun comparable to American Thompsons, German MP-40s, British Stens, Russian PPSh and PPS weapons. The Type 100 SMG was behind the curve and not really available in sufficient numbers to be worth discussion.
Their AT weapons would have been great in 1939 but by 43 and 44 they were hopelessly outdated. The Shermans that were on the light side of medium in Europe were practically heavy tanks in the PTO. I'd hate to think how Japanese 37's would have fared against Australian Matildas or Valentines if there was ever enough open ground for them to have fought a proper armoured clash. When the Russians hit the Japanese in Manchuria with IS and T-34 tanks the Japanese stood about as long as a saltine getting hit by a sand blaster.
Airplanes - the A6M Zero was a good plane early on but it's what they ended the war with. Like Iconodule says above, it was better than the Buffalos (as well as the Wildcats), but it didn't have the armour of the P40s. As the war went on the US had Hellcats, Corsairs, and P-38's, and the Japanese were stuck with the outdated Zero. They never had enough Nakajimas, and those they did were hampered by the poor quality of late war workmanship.
I have nothing much to add to Kerdy's assessment of Japanese naval technology. The Yamato had the largest guns mounted in history at the time, IIRC, but a lot of good it did them. Especially since I believe it was Adm. Yamamoto who pointed out that carriers were the future.
Tactically, there isn't much to add. The Japanese soldier was one of the better soldiers in the war, but he wasn't good enough. I think you would have found the same level of dedication in many Russian units (after their crappy start) but with a much higher level of tactical/strategic awareness and technological superiority. The Pacific was a sideshow to most of the major powers. They never put as much effort into it as they did against the Germans. Ultimately, they really didn't have to.
EDIT - The Garand really wasn't that important as far as the weapons go. The Germans did not believe that the rifle was the primary killing weapon. Every grenadier squad was issued one machinegun for a total of three per platoon. The panzergrenadiers carried one per fireteam, so SIX per platoon! Americans on the other hand issued machineguns at the company level (typically - rangers and airborne had more organic MG support). A Garand has a higher rate of rife than a Mauser but MUCH less than an MG-42...and your average company would have access to four M1919 machineguns compared to the six per German platoon (18 for a full strength company). Against the Japanese - who were more rifle based like the US - it could have made a difference, but remember, you can only fire the rifle as fast as you can effectively aim it - and it wasn't until the STG-44 that an effective assault rifle came out with the intermediate cartridge.
The main thing the US had was that it's artillery doctrine was much better. US 105s could be called in from much lower ranks than they could in other armies. They also had targeting computers which let them hit more often. German and Japanese artillery doctrines were behind the times. The Russians at least made up for it in sheer numbers of guns, but American and British (to a lesser extent) artillery doctrines were vastly superior. This hurt the Japanese as well in the Island Campaigns, as in addition to regular artillery, the US was able to hit them with ship guns as well.