The Proton Kingdom is a reference to the United Kingdom because of its size.
In Rivageders, there is a statue of Q Archduke (known in Japan as Botschafter), who is Proton's founder.
As a matter of fact, Q Archduke was seen in the original Combat Choro-Q game, in which he is the ambassador for the Q-Stein Empire. His presence as a statue in Shin-Combat Choro-Q indicates a cameo appearance.
In addition, botschafter is the German word for "ambassador".