A prominent Alternate History cliché: If the PoD is before 1871, or at least long enough before 1871, in any eurocentric timeline Germany will not unite. Ever. Instead, either the single states of the German Confederation will continue to exist as single states, with apparently nationalism never even coming up again after 1848 for some miraculous reason, or some other arrangements will be made, either involving the Holy Roman Empire or not.
The reasons for that, admitted or suspected, are manifold: A disunited Germany of course is geopolitically more interesting. Also, many AH.commers apparently feel nostalgic or “loyal”, so to say, to some of the independent German nations, mostly Austria, Prussia and Bavaria. Also, many people want to wank their own countries in their timelines, and an united Germany would be an obstacle to that: Be it Denmark annexing Schleswig-Holstein, the Netherlands expanding into Rhineland and Emsland, Poland making ridiculous claims on territories with not a single Pole in them, France keeping or reestablishing the Rhine border or the UK for less colonial competition and a greater indirect influence over continental affairs.
Of course, this cliche overlooks that nationalism was a force in Germany in the 19th century, just like everywhere else in Europe, and before the Bismarckian unification it was tied with democracy. It is unlikely the states could have continued to exist independently without a strong nationalist-democratic opposition. Of course, one could imagine a collection of authoritarian, troubled states in Central Europe, but the cliche also usually calls for the states to progress as normal.
Susano is the member who gets most irritated about this cliche, which is one of the most widespread and most accepted cliches in Alternate History.
In an interesting and rather odd twist, some have argued that a united Germany is also cliche, much to everyone's confusion.