The German Empire was what is generally considered a Federal Monarchy, with each constituent monarchy subservient to the federal government, but with significant autonomy, each having their own army and courts and laws.

To call such a system feudal is a gross misnomer. Firstly, each of the constituent kingdoms were modern states in their own rights, with their own constitutions and governments. Secondly, there was none of the vassal-liege relationship between the state monarchs and the Emperor. Each of the constituent monarchs were heads of state of the constituent states, rather than direct vassals of the Emperor. In a nation with a modern constitution, no serfdom, voting rights for men over 25 and no enfeoffment, calling something like that feudal would be wholly misunderstanding both the nature of feudalism and the governments of the German states at the time.