Austrian Belgium-Lorraine

Point of Divergence (POD)
CONGRESSE OF WIEN (1815): after "Hundred days", to "punish" France, Holy Alliance gave to Austria former duchy of Lorraine and returned former Austrian Netherlands. As a result, France has intensified anti-monarchist movement (Republicans and Bonapartists) and France began to support of Pan-Germans, seeking to create a united German state around Prussia, was made informal Franco-Prussian military alliance, directed against Austria. Uprising in 1830 in Belgium was suppressed by Austrians. Belgium remained as Austrian Netherlands

French and Pan-German revolutions
In 1848 throughout Europe a wave of revolutions known as "Spring of Nations". In France, monarchy was overthrown and a republic proclaimed, led by Louis-Napoleon III Bonapart. In Germany, pan-German Frankfurt National Assembly proclaimed North German Confederation and Prussia become its leader, which availing of revolution to gain control over Germany. Although Hungarian and Italian revolutions were crushed by Austrian and Russian army, Prussia and France continued to support of pan-Italians and Hungarian separatists. In 1851 Napoleon III became Emperor of France and made anti-Austrian and anti-Russian military alliance with Prussia, Sardinia (which sought to unite Italy) and Great Britain (which sought to halt the strengthening of Russia)