[... There are far, far too many things he can say to that, most of them rude. Must resist.]

Allow me to rephrase: you should not speak of lands you know as though others share your knowledge. Certain names do seem to repeat across dimensions, but actual historical events, the times at which different world powers rose and fell, and the identities of individual world leaders vary greatly.

As an example, the Britannia you speak of as a province is an empire on my world that vastly outstrips Rome in terms of territory and conquest. Rome itself fell years ago.