The Hapsburg crisis

This map is the result of the Hungarian revolution of 1848 are successful. This leads to Galicia and Dalmatia declaring themselves independent. Piedmont-Sardinia, spurred on by nationalist sentiment, declares it's intent to unify the Italian states and merges with all northern Italian states and later seizes all of papal territory excluding Rome. During this Bohemia and Venetia also succeeds from the Austrian Empire. This proves to be the straw that breaks the camels back, as Austria, now without half or her entire military to fight the war finally admits defeat. The Piedmont-Sardinia annexes the Kingdom of Naples, the newly independent Venetia now called Veneto, and the rest of the Papal State, forming the Kingdom of Italy. During all this Frederick William IV accepts the title of German Emperor at the Frankfurt Parliament leading to a united German Empire. Later the Crimean War starts and without Austria, the British and French fight much more viciously. The war ends with Britain annexing Crimea and the islands of Hiiumaa and Saaremaa. Wallachia and Moldavia merge to form Romania.

In short, Hungary becomes independent, every other country in AH does as well, and German and French empires exist at the same time.

Edit: redid the map to make it look better.