NAACP

Taking technical. You know very well that citizens of the U.S.A, are called American by just about every other country on the planet. Other inhabitants of the Americas are usually called by their country's name +ian.
And i was talking simplistically. Even if you can trace your heritage, the only way you could really call yourself that is if you are 100% of it. I'm African-American, I can call myself that because my parents weren't born in America.
In fact, calling yourself whatever depends on your viewpoint, there aren't any set-in-stone rules for calling your self "African-American", "Scottish-American", or whatever else there is.

Well, yeah... In your case, it would be a valid statement. However, at some point, after a number of generations, it has kind of lost its value.