Sure but...

Yes, a writer of any background can write characters of other races and nationalities but be aware of the issues in doing so. If male writers write female characters, then they should be aware of their male bias (same goes for women writing male characters) and stereotypes of women, just write them as humans with complex motives and flaws. The point of literature is to explore other humans beings and have empathy for them, so writers of whatever background should write characters of different backgrounds to their best understanding of people of different backgrounds.