What I think

I think writers should be able to write characters of other races and nationalities... on one or two conditions

1. the author in question should research the said race and/or nationalities in depth, perhaps even talk to people of the race and/or nationality and thee race/nationality's relationships with other races/nationalities

2. if questioned about a topic the author mentions in the book about the race and/or nationality, they should have have a list of their research/notes to show that they aren't just speculating or making something up

I don't know, this is what I would hope to do if I was writing a story that includes people of different nationalities