Some would call you racist, truth be told. But I don't think it's weird to not be attracted to other Races. And it certainly isn't your fault, either. Just like most females are attracted to those with British accents, it's the same thing when your not attracted to those with British accents. It can't be explain why or not. It's just who you are.
To be honest, for the longest of time I was not attracted to Mexicans. Almost all Mexican males I've ever seen were overweight and well...just very "yuck-looking", you know? Not very polished I guess you could say. But then I fell for this one Mexican pretty dang hard and have been with him ever since. He's overweight like most other Mexicans I've met but I don't know... I love him.
I'm sure a lot of people, whether they're aware of it or not feel the same way you do actually, in that they're more comfortable with people of their own Race/skin color. I mean it's really not that often you see Salt and Pepper couples, ever today when it's supposed to be okay. It seems we're still matched up by Race whether we purposely make it happen or not.
You're not weird or even racist, you're just aware I'd say. Much luck.