This has probably already come up, but I was watching The Man in the High Castle last night and one of the premises is that the USA, due to weak leadership, did not enter the war until later in the 1940's.  So, that made me wonder, would Japan waiting to hit Pearl Harbor in late 1942 have made much of a difference?  It would have likely delayed a real entrance into the European theater, and of course given the Axis powers more time to build their own forces/capture more territory.  I also wondered if given an extra year could Germany have taken the British isles, essentially taking away the best base for supporting operations in mainland Europe?

If you read into Japan's Imperial Conference, you'll be provided with unprecedented information regarding the deliberations that took place on when where why and how they need to attack America.

Economically, they could not have afforded to wait a year.

ETA: Some starter information Gozen Kaigi

I think it would've prolonged the war as our manufacturing wasn't totally committed to war production until we were really in it. We still would've been supplying the Brits but the Russians would've had equipment and stores issues without our help.
The Axis, at that time, had most of the territory they wanted until Hitler invaded Russia. Japan probably could've kept going in China without us intervening but if they went after British possessions, I think we'd have been forced to be more active — with or without Pearl Harbor.
I don't think it would've affected whether Britain was invaded or not. I don't think Hitler had a true desire to invade Britain. His eyes were on the East.
Our entrance into North Africa would've been delayed and we probably wouldn't have been able to supply the Brits with the quantity of tanks that eventually drove out the Afrika Corps.
If the Japanese had just left the British alone and just took Dutch and French possessions, maybe Pearl Harbor wouldn't have been seen as necessary.

The USN would have had more ships commissioned.  If you check out Jane's Fighting Ships, there were new battleships and the Essex class CVs that were ordered before the war and were being completed in 1942.  

While it takes time for a crew and ship to work up to combat worthiness, it meant that the IJN would have to face a much larger American fleet than it did in 1941.  Japan's ship building capacity could not keep up with the US and her training of pilots and aircrew much slower (Americans knew cars and so it was easier to train them to be aircraft mechanics, armorers, etc.).

Yeah a year would have been a disaster for them. 6 mos more would have been bad enough. Japan had about 6 mos reserve of oil and aviation fuel along with other vital resources when America put that embargo on them for all their slaughter and rape in China and Korea. And it wasnt just America, England and the Dutch slapped embargos on them from their Asian colonies so very vital stuff like scrap iron, rubber, steel, tin...ect, really everything a modern war machine needed to operate was cut off from them. The big one being oil and oil products. Japan imported almost all its oil and America accounted for about 80% of its imports. Add to that Roosevelt froze ALL Japans assets in America.

I remember 6 mos being the time limit Japan could still stay on the offensive with the embargo in place. Every day they waited we got stronger and they got weaker. American ship yards were already building a vast fleet to use against them. Keels had already been laid for 5 additional carriers by Dec. 1941.

Be interesting to see how the European theater would have ended up with a delay of a full year of the USA entering the war.  I believe the Soviets were already starting to turn things around on the Eastern front by that time.  Of course, how much did our North African campaign help benefit the Soviets in their fight against Germany I'm not sure.  Had the USA not taken needed resources and man power away from the Germans would they had been able to beat back the Soviets enough that with one more year they could have defeated them? I don't think so.  Result in the European theater would have been pretty much the same I think.  

By mid-1942, the Philippines would have been far more formidable to take - the Filipinos drafted in late 1941 would have had time to train, the US units scheduled to reinforce would have all arrived and, for example traded their light tanks for mediums and 75mm artillery for 105s.   Also, several additional fighter and bomber groups were scheduled to go.  

The US would have probably actually shipped MORE Lend-Lease in 1942 than it did, since the Army wouldn't have been racing to activate divisions that then sat around in CONUS for 2-3 years.  Historically, Marshall fought to keep as much equipment as possible for US forces to train with, without active US involvement, a lot of this is freed up (along with the shipping not taking US forces overseas).  

Also, without the Burma campaign, the Commonwealth forces that historically went home in early 42 (2 Indian Divisions, 2 Australian Divisions and 1 British Division) would quite possible have forced Rommel to evacuate instead - historically, a huge quantity of veteran troops and aircraft were pulled out right after the Crusader battles, thus giving Rommel a totally unexpected chance to recover from the DAK's virtual destruction.

So with the increased Lend Lease do the Soviets end up in Berlin before the other allies can make the Normandy Beach landing in '44?  Wondering if in that scenario more of Western Europe would have been swallowed up by the Soviets?

I doubt it would push the Soviets a whole year ahead.  The real ramp up in shipments had to wait for the Persian Gulf route to get really going, and in any case, the UK and Free French would presumably have gotten a larger share (since US shipping wouldn't be so stretched).  Without Pearl Harbor in 41, most of the US buildup towards war would have remained focused on Europe as originally planned, and any strike on PH in 42 would probably have fared far more poorly than in 41 (there would have been a LOT more then 1 radar set active, and somewhere around 3x as many fighters, conservatively, as well as far more search aircraft).  Overall, waiting a year, even assuming Japan COULD attack after a year of embargo, would have been even more disasterous than what occurred.  Also, without an attack on PH, the Soviets would possibly have kept more troops in the Far East longer, though that's hard to determine.

The embargo and the Two Ocean Navy Act set the clock ticking. Because of the Two Ocean Navy and Depression recovery shipbuilding programs, the US  commissioned 6 fast battleships in 1941-42, and  one fast carrier, with three nearing completion.  Over a dozen additional Essex class CVs , dozens of heavy and light cruisers , and destroyers, submarines were authorized and under construction. Not to mention  4-6 Iowa and 5 Montana class battleships were planned and the first two were well under construction.

Japan had to strike fast or run out of strategic commodities or be face by an avalanche of USN  reinforcements. The USN had planned to have  17 new battleships and 12 carriers  in addition to the existing fleet.

What happens after Dec  7,  if Germany and Italy don`t declare war on the US? I think that is the bigger question.

Couldn't wait.  They had a 6 month oil supply on hand, and were embargoed by the U.S.  This meant that for their war machine, already operating in China,. to keep going, oil had to be seized.  Nearest oil was the Dutch East Indies (modern Indonesia), which had the added attraction that the crude oil, straight out of the ground, could be burned in ship boilers, (although with much more smoke generated).  However, the Dutch were in a defensive pact with the U.S., British, and Australia..  That mean the battleships of the Pacific Fleet had to be taken out of the equation.


The advantages that oil fired battleships had over coal powered warships, and the need for the oil to feed them, actually set the stage for much of our current problems in the Middle East.