If we start at the end of WW1, we can use a different sort of Treaty. Germany and her allies must be the peacekeepers for the European colonial assets, against revolutions, and etc. It is supposed to take the place of reparations, so the winning nations don't get money but free soldiery. Because this treaty is signed, Soviet Russia is alarmed. Rightly so, as it is still weak from the WW1 battles, and a revolutionary government. Only Germany signs this treaty, the rest pay reparations.
But the German peacekeeper army is used more in the European fashion of sending in cannon fodder for colonial possessions, not stopping the backward Russians. With little training, the varied environments prove to be too much for the average German Peacekeeper, but those who survive 3 or more engagements can fight anywhere in the world it seems. Soon, the German Peacekeepers are the most respected of all, and independent nations are either sending their own troops to Europe to train with the Peacekeepers, bringing in money for all of the continent, and in some places where Europe is not involved, the government ask that the German Soldiers come and put down their rebellion.
The effects of this new mercenary society does not make all the Germans returning home jump for joy, but it brings comradeship from battle, hatred of the imperialist way, and a wish for a new government to resettle to debt. A socialist revolution happens in Germany, not Nazis, but instead, pan-socialists, each getting a territory to try out their semi-autonomous way of socialism.
The nations of Europe, frightened at this idea, blame the Soviet Union for subversion. This is not true, as the Soviet Union is still fighting it's own revolution and counter-revolution. But the USSR is the first to recognize this new German government.
German soldiers are still being used for the empires of others in Europe, but now the USSR is allowed on the list, as Pan-Socialist Germany knows the new economy of Europe is built on the shoulders of the Imperialist/Communist battle. Turning into a crack squadron of Winter troops is easier for Germans now than in the OTL WW2, because the Germans have the right equipment, supplied by the Russians themselves.
With the stock market only hovering, the stagnated America tries it's own socialist policy, with a newer socialist president giving Pan-Socialism the chance. All the states may choose a form of socialism. The ones that work the best are Limited Utopian Anarchy in Mormon Utah, Communist Delaware, and Anarcho-Individualist/Syndicalist Texas. However, these are only trials of the socialist methods, and capitalism remains nearly the same.
In 1939, Civil War breaks out in Spain. OTL's Spanish Civil War was larger, but this one was being attended to by the German Peacekeepers. Facsists did not sit well with Socialist Soldiers being the Watchdogs between the two, and more than a few firefights broke out because the German Soldiers were singing socialist songs and the Facsists thought they were the Spanish Communists playing tricks.
In this timeline, Spain falls to the Communists, a much more brutal form than Germany's Pan-Socialist Government, and toeing the line of the USSR, who directly aided the Communists, instead of being officially neutral like the Germans. Portugal, now near a Communist dictatorship and the agents of the comintern working their magic, quivers with anticipation for an invasion from Spain, and asks that the German Soldiers in Spain come to assist in border patrols. The Capitalist nations still on Europe pressure Germany to due so, and it complies.
The United States stock market crashes in the 1940s. Europe is affected very little, but Canada is too close for comfort, and the British want to ensure that the United States will not spill any conflict over into Canada. So, German troops are sent there aswell. They perk up the economy aswell as wait for a long time for the United States to rip itself apart.
Many states are trying to push capitalism back on their citizens, and the citizens do not like it, especially where the signs had been showing improvement under socialist reforms. With Martial Law in place the riots in the capitals of each state grow more violent as the atrocities on both sides grow. The first state in which ML was declared state wide was Columbia (not a state, but, anyways) as the reformist leaders gathered there with their most hardcore followers, and battled for the federal government's place.
The people generally lose, as they only used 7.5% of any state as an average. The rest didn't care one way or the other, and aside from the rich, people needed to work to eat, and were angrier at the revolutionaries for closing businesses when their families needed so much in the Depressed Revolt of 1940 (that's what I'm calling it). However, with the threat of the comintern coming ever closer, McCarthy is more popular in this timeline than OTL, because the depression and revolution lengthened each other for almost 7 months. Because of this millions have nearly starved, and socialism is a near taboo subject in many households.
As in OTL, the US gears up for a fight against the Reds, 'Better fed and in bed then dead and red' is the slogan, references to the DR of 1940 spicing it up a little. With the crisis visibly over, the German Peacekeepers go home, and the American Peacekeepers start up. Canadian Military Observers, who had trained with the German visitors, train the newer North American Peace Corps. with more effectiveness than either military had before. They're the peacekeeping solution to the Korean War, and this time, without world approval, the NAPC cannot hold the line, and asks the Germans to help. The Germans refuse. NAPC slowly returns the favours and advances up the peninsula, where the tides turn again as the Chinese aid the DPRK military. This get's Britains attention, and the vote is held to send the European Peace Keepers to defend Hong Kong while more assist the NAPC.
Germany says no. Advised to do so by the Soviets in Russia, the telling off of the European Imperialist nations strikes a blow politically for the underdogs of the fledgling communist nations in Asia and Africa. Europe seems okay with it, and sends it's own troops. They do well against the untrained conscripts on the Korean Peninsula, but are no match for the overwhelming numbers. European Help is believed to be too little, too late; The Americans drop the threat of an A-bomb (developed by america in 1948) on China, and while the Soviets in Moscow haven't been paying too much attention, the Chinese communists go crazy. They commit all their army to the attack and the US calls for help one more time. Seeing it in trouble, Japan takes a swing at the Pearl Harbour.
Japan gets nuked and switches sides almost right away, promised that it can have any parts of China or North Korea it occupies. Australia, seeing a threat as the South East Asian nations are slowly turning communist, joins in and helps. India gets independence in a hurry as more British soldiers are needed at the Korean Peninsula, and it wisely decides to attack the Chinese in the West as the deal goes with the British. This draws China's anger and it is fighting a two-front war now. The Soviets send tanks eastwards and try to conquer Eastern Europe, and the Germans, expecting this, manage a brilliant defense long enough for the rest of Europe to open their eyes and deal with it. But Spain then launches an attack upon France, and the Germans in Portugal are being shipped back home when many are killed in bombing runs, arrested by communist sympathizers an interrogated, or killed as Soviet military units stationed in Spain take them out.
This, hits the fan as bombs drop upon Chinese military installations.
World War 2 ITTL begins 1952, as nations of the entire world draw those lines in the sand.