Stick To The Facts
Writing about other races and nationalities can be difficult, but I think every writer can do it. The reason I think this is simply due to the fact that as a writer, we are constantly talking about things we normally don't. Why? Because we're interested in those topics, those people, those things, and we want to learn.
If you put the time and energy into researching other races or nationalities, it shouldn't be considered racist or offensive. Base your writing on facts and not stereotypes, write what you want!
If a Caucasian writer has an African-American antagonist, it doesn't automatically mean they're racist. It could be a matter of adding diversity to the book, or maybe being curious about what it is like living in someone else's shoes.
At the end of the day, if the writing is done tastefully and respectfully, people should understand it isn't coming from a negative space. When ever change has been made in history, the majority and the minority have to work together.
Writing is about uniting people, and to do that, we have to write outside our comfort zone.