Something surprises me, namely the target of Pearl Harbor. If Germany somehow would decide to attack the USA, why not doing it in the Atlantic? Germany had lots more forces and capabilities closer to their home in the Atlantic erea.
If the war was expected to have the most decisive results in the Pacific, and be largely a stand-off in the Atlantic, it would definitely make sense to start with Pearl Harbor. Germany could also inflict much more decisive damage on Pearl Harbor that it could to the East Coast (with conventional weapons). Hit the ships, planes, and harbor correctly, and you've temporarily crippled the Americans in the Pacific. Strike with even ten times that strength at the Eastern Seaboard, and you're a drop in the bucket. Not to mention that given ship traffic across the Atlantic a surprise attack would be limited to submarines or ICBMs.
I think Grey Wolf has the right of it.
German victory doesn't return the colonies occupied by Japan. With Africa dominated by the Europeans, who are in turn mostly under the shadow of Germany, and South America closer to the US and Britain (read: neutral), Asia would be the natural region for which the Powers could compete.
Germany would probably have pressured the British into pressuring the Australians into returning Germany's South Pacific colonies, and would likely have "friendly ports" in Indochina and other French colonies. That wouldn't be much of a base from which to start a general war, or even to retake its colonies from Japan. But China is a natural ally that could solve all that. Assuming the Germans involve themselves in a Sino-Japanese War, they could sweep up their lost atolls, likely lay hands on Taiwan as well, and have in China a real set of Pacific bases to work from.
Say....
No Zimmerman Telegram. American entry into the war is delayed by 10 months. By late 1918, Germans aren't pressured enough to launch operation Michael as an attack instead of a counterattack. The Entente politically has to make an offensive given Deutsch successes in Russia. When they push, the Germans wait for the assault to peter out, and then counterattack the new, unprepared defenses.
Operation Michael sweeps past Entente lines, then Entente rear defenses, then Paris. The war is over. Britain negotiates to keep France and Belgium intact -
really don't want Germans at the mouth of the Seine. As such, Germany regains its colonies in Africa and adds Equatorial Africa from France, the Congo from Belgium, Cabinda from Portugal (oh no!), and Zanzibar from Britain.
In Europe Deutschland annexes the Baltic Duchies, French Lorraine, and Luxembourg, and dominates or influences everything from France to the Crimea. Austria-Hungary becomes Austria-Hungary-Poland and, after a brief political struggle, Austria-Hungary-Poland-Jugoslavia. Hungary remains mostly intact by finally granting rights to its minorities. The Ottoman border extends to the Caucasus Mountains. Their nominal position in Egypt and Cyprus becomes real, but the British retain the Suez, some bases, and the Sudan. Bulgaria gobbles up Macedonia. Italy switches sides again and is rewarded with Denmark-sized slices of Somalia and the Sahara. Only in Asia and the North Pacific is Germany thwarted by Japan. It even opts for bases in Indochina over annexation, rather than risk the Japanese grabbing that, too.
A prolonged period of economic instability follows - booms, busts, and a prolonged recession in the early 1930s. The British turn inwards and begin discussing Federalization of the Empire. America indulges in Germano-phobia and isolationism. The latter wins out during the 1935-1936 Chinese war, leaving the American Phillipines and Hawaii threatened by China and the German Pacific. The war end with a British-mediated cease-fire that leaves Japan in Korea and no-one satisfied. Mussolini (
it's possible) participates, lusting for glory, and gets a few islands. If he's really lucky one is Okinawa.
Germany has netted itself Chinese friendship and a true colonial empire, but in the process isolated themselves from all but their closest allies. The British and Dominions cool, while the Soviets and Americans become overtly hostile. The latter begin to rapidly expand their militaries. The Russians are in Sinkiang and supporting communists in north and central China. The Americans are laying frames for an enormous fleet and supplying the Japanese in Korea with tanks.
It's clear a ruinous war is looming, but neither the US nor USSR are stronger yet in the conflict zones. Nor are the two allied. Waiting would weaken their position or even allow their enemies to establish an alliance, but a Short Victorious War [
TM] against one power.... Well, that would firm everything up.
So. They could fight a massive land war against Russia, which would rekindle the awful memories of the last war and beg the question of just how friendly or neutral the rest of Europe really is. Or.
German forces strike in force at the Phillipines, Guam, and Pearl Harbor.
If they can just cripple the American fleet, they can wrap up the West Pacific and overrun Korea before it can be properly replaced. Then the Americans will be stuck, bigger navy or no, and the Russians will be cowed. Mein gott, you guys, what could go wrong?!?