For this to happen you would need a very different buildup. A Germany that doesn't plan on competing with British Navy, a weaker France and a stronger Russia.
The British policy was to always ally with the third strongest nation in Europe, so that the second strongest could never overtake them. A stronger Russia seeking to expand into Europe would make Germany a more tempting ally, especially due to good relations, a related monarchy and no animosity because of a Germany Naval buildup. I would probably try and put France in the same positions as Pre-WW1 Russia. A large powerful nations, but strife with internal conflict and dissident. While the British have allied with the French in the past, they would probably be hesitant in France's domestic situation was less than stable.
How you get the USA involved can be done three ways. One the Venezuela Crisis goes down a bad way and leaves the USA with a bloody nose. The loss of Puerto Rico and loss of influence in Cuba. The second is the USA intervening in an earlier Russian-Sino war. The Japanese repeat their initial success, but due to Japan's alliance with the British, it is feared that Japan's success would put the USA at the risk. The USA intervene on behalf of Russia and the British intervene on the behalf of Japan. Calmer heads prevail and the USA/UK agree to end the conflict with minimal exchange of territory. Japan is annoyed by the UK and angered by the USA, while Russian relations with the USA sore ever higher. Or option number 3, a combination of the two above.
The USA and the UK need to but heads more often to lead to the sort of tension. USA allying with Russia would be seen as a definite risk to European security, while the USA would see it as securing it's own.
After that have things go down as OTL, Arch Duke Ferdinand assassinated, Austro-Hungarian Empire declares war on the Serbs, Russia jumps to their defense, Germany comes to aid Austria-Hungary, the French alliance with Russia means that they go to war with both Austria-Hungary. The British sit it out initially, but when Russia troops cross Turkey's border (You are going to need a much weaker Ottoman Empire to get the Russians to be at a strength to pull this off.), they declare war on Russia, for breaking the Treaty of Sevastopol. The USA seeing the way the war is going, the possible risks of a British Hegemony in Europe on it's security, along with pleas from Russia announce their deceleration of war against Britain, Turkey, Germany, Austro-Hungary and their allies. Japan and Italy is tempted by both sides to join the war, but Japan eventually sides with The British Empire, while Italy chooses neutrality (until the final year of the war.).
The French war effort immediately shows how unprepared they were for the war. Within months of the war start German/British offensive is within 20 miles of Paris, but it grinds to a halt, when the French start throwing huge amounts of men against the advancing troops. The stalemate continues throughout most of the war with the French slowly being pushed further and further to Paris.
In Russia their initial offensive goes well, pushing hard against the Germans and Austrians. It does not make the progress it needs in turkey though, with British/Colonial troops stalling the advance before it can reach Istanbul.
Initial fighting in North America allows the USA to make huge advances in Canada and by the end of the year most of Canada is under US control. Due to the size of Canada though, trained insurgents and rebel outfits will continue to prove an issue in the occupied territories for the rest of the war. Most fighting between the USA and the Imperial Alliance in this regions, consists of fighting in the North of the Atlantic. Germany and British navies will clash for the rest of the war with key battles being fought in the North Sea, the Caribbean and Bermuda islands.
Fighting is not restricted to the North though as French backed Brazil attacks British Guayna and British backed Venezuela. Colombia too joins the fight on the side of Venezuela. The Brazilians initial success is turned around in the face of brutal Jungle fighting. While the USA/Brazil does blockade the sea routes Venezuelan and Colombian forces exploit the Amazonian Rivers. In South America River Fleets battle for control of the important river ways to the Atlantic. Argentina and Chile maintain their neutrality throughout the war.
In the Pacific the reverse happens for the USA. Japan makes serious headway into the Pacific with the help of the British/German Colonial fleets. By the end of the first year the Philippians falls to Imperial Forces. The same cannot be said for Japan's advances in Russia. Japan immediately finds it facing a determined and well dug in opposition as opposed to the earlier Russian-Sino conflict. Though Japan has the numbers and Naval Superiority it is unable to breakthrough Russian lines.
About a year into war the USA will probably start to land troops in France. The British will probably score a lot of victories, but will eventually be forced to allow a limited USA landing in France. This will be a huge moral boost to the beleaguered French, but a moral hit for the USA when they discover how outclassed their French ally is. With the arrival of US troops the French manage to hold the British/German troops at Remis. Both sides being to dig in for a long battle of attrition.
The Second Year in North America sees the last Canadian city captured. The Canadian Government travels to Britain, while it's forces that didn't go to Europe remain to organise and lead resistance movements. Mexico is pressured by the US to join the war. Mexico seizes Belize within a week of it's deceleration. This proves to be disastrous for Mexico ruling government as the opposition groups see this as a betrayal of the Mexican people. Rebel movements popup throughout the country and the USA is forced to send troops to help the Mexican government put down the rebellions.
In the South America Theater the loss of Belize becomes a real blow to the British Naval efforts in the Caribbean. Limited to the Caribbean Islands, this becomes worse when a USA naval assault catches the defenders at Guyana by surprise. The assault it successful and British lose yet another port. Puerto Rico, Trinidad and Jamaica now become the single most important islands to the British War Effort in the Americas. In Britain the Admiralty recommends the abandonment of the Jamaica to consolidate what remains of the British Naval Assets to Trinidad and Puerto Rico. This refusal leading to the Battle of Bermuda. The British destroyers and a Battleship are caught by the US Atlantic Fleet. The resulting fighting destroys all but one of the destroyers. The battle proves to be a blow to British Moral and leads to the loss of the Bermuda Islands soon after.
In France the stalemate continues, slowly more US troops are arriving, but keeping the US troops supplied becomes more of an issue as the British actively hunt convoy fleets. Germany begins to mass troops in France to try an knock France out of the war. The German fleet becomes more committed in the Baltic sea due to the Russian use of Submersible ships to attack German shipping. Hunting these submersible fleets becomes a priority to the German Government. The Russians are unable to break the German defense of Grudziadz, while in Austro-Hungary the Austrian army is able to successfully counter attack the Russian forces at Lviv, breaking Russian liens and pushing the Russian forces to the outskirts of Warsaw. Inside Russia notable figures start to criticise the war effort, many having expected a quick and easy war. The Victory at Lviv proves to be costly to the Austro-Hungarian Empire too, as nationalist newpapers start to print the casualties of each culture.
In the Pacific Imperial Forces are held back from the complete conquest of Philippians by the arrival of a US Expeditionary force. The manages to hold several cities before being forced to withdraw to Midway and Hawaii due to rumors of an Imperial offensive being planned in the area. These rumors are unfounded but it does give the Imperial force time to consolidate it's control over the occupied territories. In the latter half of that year the USA starts to build up it's troops in preparation for an assault the occupied territories.
In Asia Japan is finally able to break the Russian defense via an amphibious landing Magdan. The Russian forces are forced to withdraw less they become surrounded. Though Japan is able to seize all Pacific bordering territory from Russia, they are unable to push any further into Russia. The Russian Pacific Navy links up with the US Pacific fleets in perpetration for a joint assault. The loss of this territory is a huge blow to Russia, now unable to receive supplies from the USA, Russia is forced to go through Iran to purchase the materials it needs. For Japan this victory revitalises the Japanese peoples support for the government and the war.
In South America and Turkey the stalemate continues with neither side able to make the key breakthrough.
The Third Year sees the USA go on the offensive in the Pacific. Over two hundred thousand US troops attack islands and occupied territory across the Pacific. At the same time Russian troops launch their offensive against the Japanese. Japan unprepared for an attack on both sides is forced to surrender the territory it had gained falling back to lines in Amur and Kharbrovsk. In the retreat thousands of Japanese troops are captured or killed. In the Philippines the US are able to make successful landing in the South, but are unable to advance further north. Another landing attempt is made on Papa New Guinea. Though the Imperial Forces put up a heavy resistance Papa New Guinea falls to US troops within a month of their landing. The Ferocity and force of the attack had caught the Imperial Alliance completely off guard. In the colonies cries for the war become louder. To deal with the US offensive the British begin to send more naval assets to the Pacific Theater. This will leave the British Home Fleet stretched.
In Europe the French and Russian armies motivated by this sudden reversal of fortunes launch their own offensives against the Imperial Alliance. France is able to push the British/Germans back only a few miles, while Austria is forced to leave Warsaw of face encirclement. The only place that did not see any measure of success for the Allies is Turkey where the offensive is not only defeated, but a promising German commander Rommel is able to push the Russians back and capture the Russian Black Sea fleet in a lighting raid on Sevastopol.
In South America the British take advantage of the USA's attention being focused in the Pacific and successfully manage to break the blockade outside Colombia and Venezuela. With supplies coming in for the first time since the outbreak of war Imperial forces in the region launch a daring attack on Guyana and Ampa, effectively pushing the war out of Colombia and Venezuela and for the first time fighting would take place in Brazil proper.
In North America Canadian Resistance fighters continue to be a problem with the US, their attacks now striking as far south as New England and Chicago. With the war dragging onto a fourth year the population Russia and the USA both begin to question the feasibility of continuing the war.
Year Five. Serbia falls to Austro-Hungarian troops. The last battle taking place in viscous urban fighting that seems much of the Serbian capital destroyed. A new weapon starts to appear in Imperial Forces, this weapon is called a tank. Slow and easy to focus artillery on these weapons become a beacon of fear for the enemy that face them. Impervious to small arms fire, the Imperial Forces begin mass productions of these immediately. Austro-Hungary launch their Spring Counter-Offensive against a tired and stretched Russian army. The attack successfully breaks through Russian lines. The Austrians using Calvary they had kept in reserve keep the Russians from being able to force a concentrated line, instead leading to Russian pockets, trapped and surrounded by advancing Imperial Forces. Germany too launches a lighting offensive against Russia, the combined forces push to less than 20 miles of St. Petersburg and Moscow. For the Russian Tsar the pressure is almost too much. His advisers begin to pressure him to arrange a ceasefire. Instead he chooses one final offensive to start at the end of the year.
France Falls in the Summer of that year. German and British troops report hearing fighting within French lines. It soon becomes apparent that the populist opposition had launched a coup against the Government without the full support of the French Military. While it could still claim to be the rightful government of France it sent an official declaration of surrender. The Imperial Forces accept the surrender, falling back to create a line stretching from Amiens to Basel. Germany annex's the territory from Basel to Nancy and Metz. The Remis Confederation is setup in the remaining territory to act as a buffer nation. All it's colonial territory would be awarded to the British Empire baring the colonies of Indochina, which would be awarded to Japan.
In the USA this is seen as a huge, but expected betrayal, with US troops already being pulled back from France a month before surrender. With the defeat of France, Germany troops are sent to support the offensive into Russia. The British use their free troops to launch their own offensive into Turkey liberating the country and going as far as the Caucus Mountains.
In the Pacific the situation slowly deteriorates as more Imperial Naval assets arrives in the theater. Forced to abandon several the Island they had taken the end of the year sees the Imperial Forces in prime position for an assault of Hawaii.
In Russia the Tsar order the final offensive of the war, The Autumn Charge. The Imperial Forces not expecting an offensive this late into the year, were caught by surprise as a million plus Russian troops attacked their lines. The offensive is a limited success, as it is able to push the Imperial Forces out of Russia in places, but is unable to achieve it's objective of taking Warsaw. The first day of the attack alone leads to the death of over 60,000 soldiers. After two weeks of assault the offensive breaks at Brest. By the end of the offensive over a 500,000 soldiers are dead. The Autumn Charge proves to the Tsar that Russia cannot win this war and in the USA the amount of casualties horrifies the US politicians.
On the 28th of November Russia and the USA ask for a Cease Fire. Brazil is only brought to cease fire when the a combined Imperial Force captures Sao Paulo.
Year Six.
The war ends the 16th of January that year, Russia agrees to surrender territory along the Baltic to Germany and that the buffer state of Poland be created under Germany control. Japan is allowed to annex all territory it currently holds in Russia. Russia creates the buffer state of Ukraine to border Austro-Hungary. Ukraine's border will stretch as far as Crimea east and Kurks in the north.
The USA is forced to release Canada and surrender is Pacific territory as far as Hawaii to Japan and Britain. Russia and the USA is forced to pay reparations numbering billions to members of the Imperial Alliance. They are also forces to scale down and reduce the amount of troops and ship at their disposal for the next ten years.
Brazil is forced to secede territory to Colombian and Venezuela, along with relinquishing all control of trade from the Amazonian Rivers. A buffer nation of Parha is created stretching as far as Amapa and Para.
Japan is the only nation amongst the victors that is not content with what it has gained. Soon after the war it's government is forced to become more democratic less it face rebellion. Elections begin later that year.
The British Empire stretched to the limit like never before it changed by it. The Colonies begin to demand independence sooner.
Germany comes out of this changed, a stronger and more powerful nation than ever. The real victor of this war.
For Austro-Hungary their victory though great was Phyric. The surge of pride for victory was not as long lasting as the Emperor had hoped. Withing two year Austro-Hungary would be gripped by nationalist crisis that would see the empire's end.
At some point my suggestion turned into a timeline. Sorry.
