You can't assume someone who has dark skin was raised in a culture that you define as "black" or not. Therefore, the label of "African-American", which is based solely on skin color, is a poor label. That has nothing to do with racism or how someone is treated in modern America.
is there really a lot of racism/skincolorism in the US? I mean, like, the guy who shot the black teen would have been as keen to shoot a black cop? in other words, one guy being in law enforcement, the other being suspicious in as much as teens running around the neighbourhood is suspicious, is a negligible difference in their eyes?
are there people who really think more highly of some pale meth addict thief than Barack Obama? of a white atheist criminal than a black Christian preacher? etc.
when you say 'how someone is treated in modern America', how prevalent is this? I mean, again, suppose these two guys walk into a cinema or cafe or book store or whatever...
would it really be skin color rather than the cultural display* that influences the response they get?
*business suit, friendly face, vs. moody skinhead-looking thuggish urban culture appearance.