Not quite star trek, but I do know that in The Man From UNCLE Illya Kuryakin, the Russian/USSR operative working for UNCLE was so popular that in the second season he got promoted from side character to full on protangonist and that aired a year or two before star trek. So if an explicitly USSR aligned spy could get that popular to the point the producers felt comfortable making him a main character, I imagine one from the far off future where Russia is more of a off hand mention in comparison would be even less controversial