[He waves a hand at her dismissively, and then holds up his index finger in a universal gesture of "hold on". The laughter tapers to chuckles after a couple of seconds, peppered by heavily-drawn breaths.]

Oh lord-- you can't be serious. France couldn't even hold onto the colonies that were weaker than him at that point, much less conquer the only one with an empire larger than his. [...that explanation was interrupted by a laugh or two here and there, but not uncontrollably so.

And yeah, the implication in that statement is that his empire was the largest in the world. But he hasn't really made the connection yet that that may not be the case in Britannia's world.]