A little simple to lump all the German states into "The German Empire". Maps like that always make me wonder who controlled the other areas? Modern Georgia and Kazakhstan for example?
Holy Roman Empire, I suppose, noting that Bohemia and Silesia are shown as part of that while Austria and Hungary are outside the bounds of the Empire.
As one of the most important States of the war: there is no Saxonia on the map. Don't forget the swedish campaign in Saxonia after the battle of Klissow!