Here's a map. The POD is that in 1914, the Schlieffen plan is carried out as originally conceived, so the stronger German right flank utterly smashes the BEF, and encircles Paris from behind. Paris falls and the French armies are trapped and destroyed in Alsace-Lorraine, leading to the capitulation of the French government one month after the declaration of war. The low countries are annexed into Germany, along with the rest of Lorraine.
Germany quickly transfers her forces east to face Russia. Several swift invasions secure key regions, including the Polish salient, the Baltic region, and Moscow itself before the Russian army can be fully mobilised. The Czar sues for peace, and his humiliating defeat leads to Germany's annexation of Poland and the Baltics.
Meanwhile, Austria-Hungary has broken through the Serbian lines with heavy casualties, and with German help, now encircles their forces and destroys them in detail.
Britain fights on alone, winning several victories in the various colonial fronts, but is finally forced to a compromise with the German Empire. In the treaty of Antwerp, both countries retain the territories they hold at the end of the war, resulting in Germany losing some territory in Africa, and Britain recognising Germany's hegemony over Northern Europe.
The Belgian government fled to Congo, where it rules with an iron fist.
In the postwar world, Germany has become a major industrial power, rivalling Britain and the USA.
Austria-Hungary has enacted a series of reforms, reducing the power of the reigning monarch slightly, and becoming a federation of four distinct states; Austria itself, Hungary (including modern Croatia and Transylvania), Bohemia-Galicia, and Bosnia-Serbia. This has stabilised the Empire, though Bosnia-Serbia is an unstable region, and Imperial troops are only just keeping order.
In the aftermath of their humiliating defeat, the Russian people have turned against their leaders in a bloody uprising, though no sooner had they forced the royal family to flee, than they began squabbling amongst themselves, moderate socialists and capitalist and nationalist republicans setting themselves against the more hard-line socialists, communists, and syndicalists. Their fragmentation lead to their weakness, as the Finns broke away, establishing the Republic of Finland in the Grand Duchy of Finland and Karelia, Central Asia becoming a loose federation slightly friendly to the British, the Ukrainian People's Republic and the Federal Republic of the Ukraine fighting for dominance, and Germany sponsoring the return of the Royal Family to set up the puppet Czardom of Russia around Moscow, and Siberia setting up the Republic of Siberia and doing completely their own thing.
France, also humiliated in the war, fell to an extremist socialist uprising in the early '20s, leading to a purge of the Bourgeoisie and middle class intelligentsia, culminating in the People's Democratic Republic of France being set up on the mainland, and the Sixth French Republic being proclaimed in Algeria, Corsica, and France's other colonial possessions, excluding North Africa, which was decolonised by order of the Treaty of Antwerp.
The Ottoman Empire also fell prey to socialist uprisings in the Twenties, with the People's Islamic Republic being formed from Northern Anatolia and Mesopotamia. Britain moved into Palestine, where a military junta had established itself, ad defended it from the Socialists, as well as forming protectorates over Yemen and the Republic of Arabia.
As a result of the political uprisings, along with several other factors, the stock markets collapsed on July 25 1925. As national economies fell and millions began to starve, another wave of unrest his previously stable countries. Britain narrowly escaped a military coup, but Spain was torn asunder by revolutionaries. In Spain, the fighting was confused, and there are reports of neighbours actually turning on one another, but when the situation stabilised somewhat, the revolutionaries held the north and west, and were backed the the French Socialists, while the loyalist forces held the south-east and Spain's overseas possessions. A ceasefire was agreed in May '27, but there have been numerous exchanges of fire along the front since then, and only international pressure has kept Spain from exploding once again.
China also suffered from the economic downturn, as a Marxist leader united the people of several southern provinces behind him and began to take control of the rest of the country. He was stopped only because in his arrogance, he ordered his troops to fire on British troops in Hong Kong. Hong Kong fell, but the might of the British Empire and it's Indian Raj descended upon him. Southern China was flooded with British forces, uniting or destroying the warlords of the region, and confining the Marxist Chinese to his seven original provinces, though there is a continual state of alert along the border, and Britain maintains a strong presence in the region. Japan also got involved in China, setting up a puppet state in Manchuria.
The US, particularly hard his by the crisis, saw a far right wing government take power and attempt to appease the populace with a military adventure in Mexico, where a puppet government was set up and billions of dollars were taken by the US as 'reparations'.
Using the border dispute as a pretence for war, Italy invaded Abyssinia, deposing Selassie, and setting up a protectorate over the nation. Britain turned a blind eye to this, along with Italy's annexation of the ex-French colony of Tunisia in return for a favourable trade agreement with Italy.
The British Empire has come to see the German Empire as a strong and stable ally on the continent, and has, with their co-operation, set up the League of Empires, comprising the British, German, Austrian, Chinese, and Ottoman Empires, along with Italy, the Republic of Ukraine (an Austrian puppet) and the Czardom of Russia.
International Socialism has established the Union of Marx, comprising the People's Republic of Ukraine, the People's Democratic Republic of France, North Spain, Marxist China, the People's Islamic Republic, and Finland, which fell to socialism in 1928.
The USA is a wild card. Heavily militarised, and far right wing, it is currently satiated by it's ventures in Central America, but some hotheads are calling for a war to unite all of North America under their 'democratic' rule.
The map shows the world in 1935.