How would have WW2 played out if Germany and Itally had not declared war on the USA?

As many of you know after the Attack on Pearl harbor the USA only declared war on Japan. On December 11th Germany and Italy declared war on the USA and then we recepricated. My question is if Germany and Italy had not declared war how differently would have the war turned out in both the Pacific and European Theaters?

Now I am not saying the USA doesn't eventually declare war against Germany or Italy to aid the UK and USSR, but what would have maybe happened had it not happened when it did?

How would have WW2 played out if Germany and Itally had not declared war on the USA?opera ticket

I'm going to have to disagree with the last two answers in some respects, firstly, how would Germany have invaded Britain? When was the battle of Britain and when did the US enter the war? Secondly, Germany was already defeated in North Africa by the time the US entered that theatre. The US would probably have defeated Japan quiker whilst still supprting the allies materialy as they had been for most of the war. Italy would have probably fallen, just slightly slower. Don't forget that the main contribution the US made to the allied war effort was material and economic more than miltary know-how, skill or indeed strengh. After Patton's egotistical race across Sicily, the Americans strugled in Italy. It was the British, Empire (Austarlian, New Zealand, South Africa, Canada, Indian etc), Free French, Polish and many more who won the greatest victory's, eg, Monte Cassino. When the US first enterd the war inb Europe they shoed their niavety and lack of military skill on mant ocasions, day bombing and gatting badly mauled by and already defeated romel in Africa. The Normandy landings would have happend on time, the US no doubt making it possible by material means. Without their aid in money and bullets the allies would have struggled. Assuming money and bullets were forthcoming from America the Normandy landings would have gone pretty much as they did. You just have to look at the progress the British and Empire forces made whilst the Americans were still on the beaches, this is inspight of greater German resistance and atention.

It is easy to think that the US was as big a world power as it was in the years following the war. This is simply not the case. Don't beleive hollywood, GI Joe didn't win the war all on his own.

As for the far east, with America acheiving victory more swiftly against Japan, therefore not allowing the USSR to storm through Manchuria and seize North Korea it's unlikly the peninslar would have been split therefore no Korean war, no rise in power of Chine, possibly (very big IF here) no Vietnam.

As for this "The United Kingdom, minus its former colonies, but perhaps including part of Northwestern France" and " Greater China, encompassing China and some of the former Japanese islands southwest of the four main islands" buisness, I'm sorry but things like that belong in Alternate History Novels by the likes of Harry Turtlrdove. Entertaining though they might be accuracy and balance are not their strenghs. More research from a less biased background needed.

How would have WW2 played out if Germany and Itally had not declared war on the USA?pacific theater opera theater

It's possible we would only have fought the Japanese. But note that the J's were allied with the Germans, so it was probably just a matter of time before we were actually fighting the Germans.

And once we were on the war footing against J, the American people probably would have been prepared psychologically to fight the Germans, and to declare war against Germany, as well.

I think the fact that G declared war against the US before we declared war is probably an unimportant technicality that is not all that important to the war.

But of course, no one really knows.

A later declaration might have prolonged the war. Operation Overlord itself (the Normany invasion) was itself put off, and it might have been put off even longer.

No one ever gets to the bottom of these speculative "ifs" that attempt to rewrite history.
Nothing would have changed both Churchill and FDR knew Germany was strongest of the axis thus war with Germany inevitable and they still would defeat germany before Japan.

If germany didn't declare war on that day USA would have.
We might not have had to drop the bombs. Perhaps we would have had time to fight the Japanese BEFORE having to turn our attentions to Europe and North Africa.
Somebody's done their homework by remembering that Japan declared war on the USA first and Germany (in an about face of Hitler's policy of only keeping alliances until it was to his advantage to break them) followed its Tripartite Pact obligation and did likewise! For that alone, I salute you.

Now to your question ... if Germany hadn't declared war on the USA (and Italy followed suit), we would most likely see a Third Reich holding Europe much longer than it did in our own history, including the UK. The USSR would most likely have not become Hitler's next target because the UK would be a logical springboard across the Atlantic.

But the United States would then be concerned with fighting Japan, ending a war with four distinct theatres of influence. Germany, the USSR, the US, and Japan would likely remain locked in a cold war for decades because the impetus for the atomic bomb (a two-front war, such as the US found itself in) would not exist.

Picture a world war with casualities akin to proposed Operations Olympic and Coronet for the land invasion of Japan (which never happened BECAUSE of the atomic bomb) in each major power and their proxy states -- figures of about a million were bandied about as casualties. That's what would most likely happen had Germany and Italy not blundered as they did declaring war when they had no need to.
There would have been several major effects:

The United States would have devoted nearly all of its military and manufacturing capability to defeating Japan. In all likelihood, rather than being forced to surrender in August of 1945, Japan would have been defeated sometime between late 1943 and the middle of 1944. During that time, Germany would have been able to devote its forces on the Western Front to defeating the forces of the British Empire and the French resistance after prevailing in North Africa, controlling the Mediterranean Sea and cutting off British shipping. So long as Hitler persisted in attacking the Soviet Union he would be unlikely to prevail - but the Soviet Army would have been harder pressed than it was without the U.S. participation in the invasions of Italy, France and the Low Countries drawing off significant portions of the Wehrmacht. In all likelihood, the USSR would have defeated Germany in the middle of 1946, and the world would be divided into these sectors:

1. The Greater Soviet Union, encompassing all of the USSR, Eastern and Southern Europe.

2. The United Kingdom, minus its former colonies, but perhaps including part of Northwestern France.

3. Greater China, encompassing China and some of the former Japanese islands southwest of the four main islands.

4. The Greater United States, encompassing the U.S., Japan and most of the island chains of the Pacific.

5. Greater Australia, encompassing Australia, New Guinea and perhaps New Zealand.

6. Other states in North and South America, Africa and Southwest Asia more or less as they are today.

(Note: This IS, indeed, an attempt at alternate history. )

The most important thing to recognize here is that under nearly any possible scenario Germany was doomed to lose to the USSR if it invaded it. One can speculate on what would have happened if Hitler had not done so, but the fact is that it was in his nature to do so. If he had not been a racist madman, he would have been entirely different - but he was not.