Are you sure from the viewpoint of a prosperous citizen of the empire that there was actually a big gap between these two comparisons? My readings have always suggested the two viewpoints would be thought synonymous.
the big gap you claimed was between “the empire I’ve known forever is going away” and “this world might not be habitable in a century”. My statement was meant to indicate that I am not sure that a citizen of Rome would have the same understanding of those two concepts that an American today might have, although there might be other correspondences between the two, the understanding of a world outside their empire being meaningful enough that its destruction would be significantly worse than the destruction of Rome.