Sophist nonsense. One seems to forget the extensive merchant trade system. A system populated by common men, men with no more nobility than a ship captain, perhaps. Go research bills of lading. Understand that they are present in every language. Understand that literate men were necessary to correctly divide loads, not only coming off the ships, but also on the wharves and in the warehouses... The same applies over-land, where huge merchant wagon trains went incredible distances through foreign lands, buying and selling as they went. Try to understand why it was that Rome's main opposition always seemed to be 'itinerant' dye-makers, tent-makers and such. And understand why Rome, with all her might and control, was never able to quell them.
The American melting pot is the exemplary evidence of this - when left to it's own devices. With bureaucracy and control reduced to it's minimum, enterprise trumps empire every_time. A common language is indeed helpful, but certainly not necessary... Although it is singularly necessary for empire, and central control, which is precisely why YHWH confounded the languages at Babylon.
Latin was the language of Rome, the capital of the Empire. It was the prestige of Rome that made Latin the language of the West. It was also the vernacular of the diocese of Rome, and after the second century the language of the liturgy. Even after Rome ceased to be the political capital, the language, culture and religion of Rome continued to have great influence. The German tribes became romanized just as the Celts had before them. The German Reich, which last a thousand years, came into being when Kaiser Carl was crowned by the pope to continue the Roman legacy in the West. It ended when Napoleon ended the Reich and himself assumed the title as Emperor of the West and he had hopes of making Constantinople the capital of a restored empire with himself as the new Augustus. Of course, this empire would have had French as its common language. But of course this all came to naught in the snows of Russia as the new Caesar sought to defeat the forces of another Tsar.