I believe that there IS a distinct difference. And that difference lies in how an individual identifies himself/herself. There are certainly groups of minorities who may identify with being "black" (for example, persons of Haitian, Jamaican, Antiguan roots, etc.) whose roots may not necessarily be from Africa, but native to another home country with people who still have pride in their heritage and identify themselves as part of the 'black" race. The terms to identify this particular group, of which I am blessed to be a part of, has evolved over the years from "colored" to "negro" to "black" and "African American". If I'm not mistaken, the term "black" became popular around the Civil Rights Movement in which many blacks wanted to instill pride in their race - for who they were, what they were contributing, the struggles that they faced being black in America and for what rights were being denied them. So, in essence, the pride aspect also encouraged a searching of ones roots, which inadvertently lead back to their ancestors in Africa. Many blacks refer to themselves as African American based upon their roots in Africa and their current roots in America. Many use both terms interchangeably but I believe that it is truly a personal choice as to what each individual references in regards to their race, be it "black" or "African American".
I hope this helps. I am by no means, an expert, but wanted to clarify my feelings on the subject!
If I have in any way offended anyone, please accept my apology.
kllee