Anna Mwalagho used the classic comedic device of repetition to hook this same sentence into multiple jokes in her one-woman show, “Never Thought I Was Black Till I Came To America,” on Thursday evening, and each time warranted louder applause than the time before. She walked onto the stage, suitcase above her head, dancing and singing in Kiswahili, her stunning voice reverberating around the walls of Oakland Museum of California’s James Moore Theatre, every molecule in the room gravitating toward her.