What a topic!!! How to handle it?
In Latin America there is a lot of racism too... so what's the problem?
Besides... I think Japanese worry more if you are Filipino, Korean, Chinese... they know about that.
I doubt that most Japanese could discriminate (in the sense of "differentiate") between a Brazilian or an Argentinean or a Chilean... and if you look "Caucasian" (but not from Grozny
), most people will assume you are an "American" (from the USA)... that's a point discussed here now and then.
Practice your Japanese. That will make a difference.
I am a Mexican, so I am Latin American too. And I will not say if I look Amerindian or White... since that differentiation is stupid to me: Your own racism and prejudice could be easily go with you, wherever you go. So be careful.