Your example comes from 1881, about 75 years before the US would become anything close to a superpower. So the simplest explanation is that the French simply ag

Your example comes from 1881, about 75 years before the US would become anything close to a superpower. So the simplest explanation is that the French simply agreed that it sounded weird in English to have it on all official letters, in stead of a superpower bullying it's allies into submission.