In 1941 the Japanese army had 1.7 million men in 51 divisions. During the Pacific War this was was raised to some 6 million men. Of course at the start of the War the bulk of the army was either engaged in fighting the Chinese and guarding against the Russians. Only 11 of the 51 divisions were immediately available for fighting in the Pacific. This is somewhat comparable to the US. The US had started their peacetime draft and by Pearl Harbor had roughly 1.5 million men in the army. The US would peak at a bit over 8.2 million men. Only a fraction of these men saw the Pacific though. And far less than 11 divisions were immediately available in Dec 1941.

Navy wise they were fairly well matched. The US had:

• 17 Battleships (+15 under construction)
• 7 Fleet Aircraft Carriers (+11 under construction)
• 37 Cruisers (+40 under construction)
• 171 Destroyers (+181 under construction)
• 114 Submarines (+79 under construction)

The Japanese had:

• 10 Battleships (+3 under construction)
• 6 Fleet Carriers (+10 under construction)
• 33 Cruisers (+40 under construction)
• 99 Destroyers (+62 under construction)
• 63 Submarines (I don't know how many under construction)

So the navies were largely comparable with the US having slight to significant numerical advantages in every class. The Japanese however had the advantage of not needing to patrol the Atlantic. They also had the advantage of generally having ignored the treaty requirements. So their heavy cruisers displaced something more like 14,000 tons, rather than the treaty limit of 8,000 tons. This helped to counter some of the numerical problems.

By the time of Pearl Harbor, the Japanese were neck and neck with the British navy for the second most powerful navy in the world after the Americans. During the war, the Japanese proved to have a problem completing ships on schedule while the US actually ramped up production and accelerated warship production. But in 1941 they were close in total strength.

Economically Japan was just behind France in GDP and production of most manufactured goods. They were well ahead of Italy in the same. They were basically the 6th greatest economy in the world. They were also spending more of their GDP on their military (partially due to the Chinese war). That meant they were punching well above their theoretical weight class.

They were absolutely considered a world power. They weren't anyone's top concern (except maybe the US Navy's). But they were on everyone's radar as a potential concern.