Mr. Tkatchev has repeatedly stated that African-Americans are a distinct nation within the United States. That has never seemed right with me. Mr. Nathan has claimed that one's nationality is defined by one's passport. That seems to me like a weak distinction.
It is indisputable that most Black Americans have different cultural norms than White Americans. I would say this defines two ethnicities, or maybe just two cultures.
I say that your nationality is defined by pledging allegiance to a governmental and military entity. For this reason, I say that Blacks are not a separate nationality.
A true existance of dual nationalities within the USA is what led to our civil war.