"...legendary Russian science fiction writer Issac Asimov..." is what they actually wrote. He's almost as well known a writer as J. R. R. Tolkein, or Ursula Leguin, after all.

But, he was born in Petrovich, so there's certainly a sense in which it's technically correct to refer to him as "Russian," though "famous Brooklynite science fiction writer" would be my own preference.