Fascinating update. It's nice to see a stable Austria-Hungary analogue emerge, most TLs seem to focus on the different ways it can fall apart bloodily.
Ooh, teasers about the coming European cycles of war and peace. Let the speculation begin!
So we know the Unification War and the Patrimonial War will happen more or less at the same time, in Germany and Italy respectively. Austria seems to remain mainly neutral, which means either A) the war doesn't affect the Hapsburg Kingdom of Italy or B) said Kingdom will have completely separated from the Austrian/Danubian complex at this point. The trend seems to imply the latter, which jibes considering that at this point, Italy is basically only made up of the KoI, the Three Sicilies, and the rump Papal State, so it would seem that the conflict will be one between the two major powers over control of Rome.
"Patrimonial" must relate to the Papacy somehow, but I just don't know enough yet to extrapolate in what manner, specifically. The crux of the conflict will definitely be centered on the Papal States and will probably be waged by other, larger powers, but I doubt that this will be a resolution of the two opposing claimants to Italian nationalism. If it were, the war would have a name like "The Italian Unification War" (in relation to the contemporary German Unification War) or the "Great Italian War".
Onto the Unification War. From previous updates, we know that Flanders will be involved or affected, and as it's implied that Austria just narrowly escaped getting drawn in, it will be a Germany-wide deal. German nationalism is alive and kicking, so this war could happen a number of ways. It could start in the Saxon client kingdoms, protesting Saxony's domination of the Bundesliga and advocating equality for all Germans. Or it could start with Saxony pressuring Swabia and/or Bavaria into joining their league. Or it could start with Saxony trying to annex its clients... Etc. I'm sure Thande will spring something fascinating and unforeseen out of the left field.
So we know that the Great American War will have a theater in Europe, or at the very least involve some of the European powers. France is the most obvious contender, given Louisiana's precarious situation in the midst of Carolina's rumbles of secession, but Spain has a high likeliness of being involved too. I'm sure Britain will get involved somehow and make a huge mess of things, again.
All of that sounds exhausting, thank goodness we'll have the Long Peace afterwards. The nomenclature implies that it will begin after a vicious round of wars, which reinforces all of my baseless speculation. Hopefully after this the European political situation stabilizes some and industrialization really takes off, during a period of political development and consolidation.