sugarcane sweet deserts her hair golden her feet mountains her breasts two Niles her tears. (2-6)
Animating the geography of Africa allows the speaker to present it as something (or someone) with whom the reader could fall in love. And after all, love is one of the key elements of patriotism.
remember her pain remember the losses (19-20)
These lines read almost like a command: the best way to serve Africa as a spiritual nation is to remember the ways blacks were treated in the past. The repetition of "remember" makes these lines almost incantatory – it's like Angelou is trying to lull us into doing just what her speaker commands.
Thus she has lain Black through the years. (7-8)
These two lines make the "citizens" of Africa clear: anyone who is black shares the history of (and thus the relationship with) Africa that Angelou describes.