I present to you:
The Riverine Confederation of European Worker's Republics (RCEWR).
Basically, Friedrich Wilhelm III.'s (Napoleon equivalent)'s Empire lasted against the diverse coalitions after the Prussian, and later German, Kaiser successfully, instead of going bananas and invading Russia, sinks the Royal Navy by supporting the Americans(?) against the British in the War of 1812, took over the French channel coast parts (forging an alliance with Aragon) and then invaded the British Isles. This led to the downfall of Britain (result on the map: the diverse autonomies and so on) and to a lasting
Mitteleuropäisches Reich and
Seineföderation (Federation of the Seine=German equivalent to the Rheinbund). But Russia got stronger and stronger, allied with Austria-Hungary and wanted to get rid of the German menace forever. This plan went terribly wrong in 1835-1847, and Germany was the hegemon of Europe ever after, busily Germanifying the French, Polish and Italian lands... Guess what?
This ended badly, namely in internal revolution and civil war from 1883-1896. And the revolution was an Equalist one. This means, yes, somewhat communist, but it is more the French Revolutionary ideals writ large: Equality, democracy, fair wages, good working conditions, and, that is new, preservation of every culture and religion. Summed up in the Wahlspruch
Freiheit, Gleichheit, Brüderlichkeit
And these Equalists led to all the confusion. They demilitarised several zones (Illyria, Poland, the Rhineland, Alsace-Lorraine), established Autonomous Cultural Nations (ACNs) for the Bretons, the Basques, the Catalans, and placed big cities (first only Paris and Berlin, but then further areas) under Special Administration. To honour Friedrich Wilhelm III., Corsica was put under Honourable Special Administration, treated like a city, renamed Friedrich-Wilhelm-Land.
The Papal State area was put under the administration of the Pope, who had to follow all secular laws from Berlin (or at least recognise acts performed under such laws, e.g. the fact that civil marriage is legal), but could dictate all canonical laws. Also, important ports were put under the direct control of the General Secretary of Transport and Trade.
But basically, except for the GSTT-controlled port areas, every area administers itself mostly, but has to adhere to all laws from Paris.
This state has it's own two puppet states: the Worker's Republic of Denmark is an ordinary Equalist state. The Jewish Worker's Republic of the Six Sicilies, however, is a mess in itself. This state came about when, once again, a Russo-Austro-Aragonian (by establishing Basque and Catalan autonomies provisionally, the RCEWR had alienated Aragon who wanted Aragon to reign supreme) Coalition tried to fight the Equalists and get some
Lebensraum. Unfortunately, Austria-Hungary was under a certain Adolf Hilter who was extremely antisemitic and wanted to kill all Jews on the Earth by means of Genocide. Aragon was under no better a leader with a certain Javier Hernandez Torres. The RCEWR, as the Equalists called their state, was allied with the (rump? Ottoman Empire, Mexico and New Poland.
Not only did many Jews remain or flee to Salonica during the war, but also to the RCEWR many sought asylum. After that war which was disastrously lost by Austria-Hungary, Torres's Aragon and Russia, the RCEWR gave it's southern puppet state to the Jews. The Basque, Occitan and Catalan autonomous zones were reinstated in their "proper" places.
By now, the Six Sicilies are a Jew-Apartheid dictatorship which massively "encourages" (sometimes forces)
Aliyat onto it's fellow Jews; with only few and barely habitable "Autonomous Nations" (read: Bantustans) for the originally native Italians and Muslim Arabs.
The rebellions in the RCEWR are of newer date, and come from three groups: Polish nationalists want to finally reestablish their homeland where it once was, autonomy for them (which they do have) is not enough. These occasional attacks or riots are taking place again since the 1980s. Militarist extremists have recently cropped up since the 1970s, their thinking being that to remain great, the RCEWR must not go down the route of pacifism, but that of war and whose dream and first act it would be to remilitarise the DMZs. These have recently committed various terrorist attacks on government officials and rioted in several major cities. Last, but not least, there are Catholic ultra-extremist rebels (since the huge revival of Catholicism in the southern RCEWR in the 60s and 70s) in the PSAZ (Papal Special Administration Zone) who want to establish, in the best case, a vast Catholic Empire, but whose first aim it is to have the Papal states secede.
To make it worse, Austria or what remained of it after *WWII claims the Saxon and Silesian EWRs and supports the Catholic extremists.