And his mother is a French, if I remembered it correctly.
Vivian Wu came to America when she was 20, Luoyong Wang 27. I guess it is easier to get rid of non standard accent while singing than speaking. I also searched a few video clips with Joan Chen (who also came here at the age 20, and she was Foreign Language majored before she left China) acting/interviewing in English. They all speak very very good English, but it sounds Vivian speaks the most fluently.