Well black in America means black Americans because they forcibly had their languages, religion, culture and nationality stripped from them. Once they were forced to speak English and convert to Christianity they were no longer Hausa, Wolof, Yoruba, Kongo, Serer, Nupe, Igbo, Mandé and the like, and in successive generations it was lost. While there are things like Pan-Africanism, in Africa today ethnic and tribal identities are still very real, and sometimes more important than nationality. A lot of ethnic groups cross national boundaries. Just being "black" isn't as important as being Shona, or Zanzibari, or Azande, or whatever. Indeed their languages and cultures are further apart than most European languages.

"People of Color" is even dumber because it lumps together anyone who isn't white or Western, as if a black man in the US has the exact same experience as a Japanese person, or a Native American, or a Panjabi Sikh.