I've already seen this once before in my dashboard, so it's obviously a popular topic to tackle with X in the A-Z.
Out of all the books you've read, how many had white girls in pretty dresses, or a white family looking distraught, or a white guy brooding on the front cover? Quite a few. Someone did a graph of all the nationalities of people on the cover of YA books a while back. I can't remember the exact figure, but the landslide was in favour of white people.
When the Hunger Games trailer was released, and people saw that Rue was being played by a girl of colour (even though this fact is stated in the book) there was an uproar on twitter, started by one girl who had stated something along the lines that she didn't feel any sympathy for Rue's character because "she wasn't white".
The problem comes from many angles, with both readers and writers tending to suffer (even subconsciously!) from a touch of xenophobia.
But what's the solution? Is it to put characters of different nationalities into your book, stating the colour of their skin in big bold type so that the readers know for sure that you're not being xenophobic?
Short answer: I don't know. Long answer: I still don't know.
Is there even a solution to be had? Some writers write about what they know, about places like the one that they live in. I live in a rural area of Ireland. Even at my University in the capital of Belfast, I would say that fewer than 5% of the students are NOT caucasian. The most ethnically diverse place for me is my television screen. Does this mean that I have a duty to make sure I deliberately put people of different ethnicities into my stories?
I still don't know. It's a sensitive issue, and I would love to hear your opinions.