Who says the Mongols didn't leave anything lasting behind?

So I’m taking a class in Russian in Paris. Now, Russian is a very beautiful language, but it has one letter, one sound, which as my professor puts it, “makes foreigners cry.” It’s even worse than hearing French people trying to pronounce the letter “h”: the written letter appears approximately like “bl,” and it’s impossible to describe the sound, since there is no European-language equivalent, except to say that if someone punches you in the stomach while you are pronouncing the sound “ee” you will have a suprisingly similar result. Rather than bask in the impenetrable idiosyncrasy of such a linguistic quirk, my professor apologized while disclaiming responsibility for it. She claims that it’s not a Russian sound, that it is borrowed from the language of one of the Tartar or Mongol tribes that conquered Russia during the Middle Ages. I assume this is why the sound does not exist in many of the Southern Slavic languages. Well, now every time I pronounce the sound (which is pretty often—it’s the plural ending for most words) an image of burning villages and madly cackling horsemen always springs into my mind. Why, oh why, when Peter the Great was Westernizing Russia, could he not have taken time off from shaving off people’s beards to expel this barbaric Asiatic sound from the language?