Kamar Taj - where Dr. Strange went to learn the mystical arts - is in Tibet.
Why do they have to mention his nationality or ethnic origin? (If that indeed was such a huge issue as to FORCE them to change the character's gender?)
P.S. if Marvel was so worried about offending Chinese sensibilities, then does it make sense to change the Ancient One (Sorcerer Supreme over all the Earth) into a woman, considering that China is still a largely patriarchal society wherein women are expected to be subservient and submissive?
I call Marvel's statement on their motives of not wanting to offend China debunked!