re: African-Americans
African-Americans, though an amalgamation of various African ethnic groups, have effectively become their own unique ethnic group. Their shared history, culture and language (ebonics) marks them as a new people on the world-stage. Of course, debates about the definition of what an 'African-American' is remain - it's quite clear that you are a distinct people. Bear in mind, what there is no ONE definition of an ethnic group. For example, are Alawites in Syria an ethnic group? Or Jews (given in mind Sephardic, Mizhraim, Ashkenazi and Beta Israel)?
If you are attempting that African-Americans are a race - I'd think you'd just hurt your case. Igbo and Yoruba are arguably from the same race, but they're different. Yoruba and African-Americans are arguably of the same race, but they're different groups.
re: Phenotype
What you're saying isn't clear here. Do you mind rephrasing your point?
re: Ethnic nationalism
A lot of significant ethnic minorities don't have their own countries, but look at what's happened to the Oromo, Igbo, Kurds, Maori, Hmong, Rwandan Tutsi before 1994 and Jews before 1948...