If I’m understanding your question, and can rephrase it: why do people have accents?
Up until about 8 months, all human babies give equal attention to all sounds in all languages. After 10 months, babies will start selecting the human sounds they hear around them and start trying to imitate them. From there on, we start hearing less and less of a difference in sounds and therefore our ability to reproduce them. These abilities are not lost forever, but it takes time to train the ear and speech organs. A native speaker of Russian may still carry over distinctly Russian phonological features when speaking English.
This paper may have some more specifics on the unique sounds of Russian and English: http://www.ijeionline.com/attachments/article/63/IJEI.Vol.4.No.5.03.pdf
