Windenburg is not only based on Germany. There is also a Scandinavian influence. The Lykke center is named after the Swedish and Danish word for happiness (The word Lykke exists in both languages but means nothing in German). Some of the names are Scandinavian like the Bjergsens with the typical Bj sound. The windslar neighborhood also has a British feel with the stone walls next to the roads. The amount of water on the map is also out of proportion if this world is supposed to represent only Germany. The biggest part of Germany is not a coastal region. For people living in Southern Germany the Italian coast is even closer than the German coast. On top of that the 'Pan' in the Pan Europa night club also suggests it is mean to represent a boader part of Europe not just one single region.
In short there is a heavy influence of Germany but it is not the only influence. Because of the Scandinavian influence I think the crumbling Isles are supposed to inspired by a Scandinavian island.
