I've been in the US around 20 times, with entry ports: Los Angeles, San Francisco, Orlando, Washington, Charlotte, NYC, Guam, and Dublin (europe), and never had any issues while flying to US to do time building, even if carried my flight bag with me, and although not black I'm dark skin and perhaps close looking to Mexican (I'm Spanish), and never had any single issue more than regular questions, that how long you will be here, do you have a job back home, and why US, and what are you going to visit while here..