Dragonflow
Emperor
Thats not true..
in the time Prussia ruled the german states where part of the Holyromanempire.
Later on Prussia and Germany became one state. And after WW 2 Prussias parts where given to Poland and Russia.
Its like saying you cant have the irokes because they belong to America now.
Prussians were/are Germans, not some completely different racial or cultural group like the Iroquois.

Only because they had a state doesn't make them a civilization, otherwise we might as well start talking about including Burgundy, Leon, Bavaria, Yorkshire, Saudi-Arabia and the CSA as civs.