The Emperor protects. After the 30-Years-war the great majority of german states had no significant armed forces, leading to a distinction between unarmed and armed states (Saxony, Bavaria, the Palatinate, Brandenburg-Prussia, Braunschweig, Hannover and of course the emperor himself) within the empire. The unarmed states were in many ways highly dependant on the emperor (and in no real sense sovereign) - the most prominent being protection against french agression. Beyond that there's the old EU-comparission, which going by Whaley doesnt seems to be so absurd: great numbers of common policies (economics, security [Polizei]) and others, though they never achieved the monetary union, both through the Reichstag on national level aswell as through the imperial circles on a regional level.