Well, Doomfist isn't American for starters so I don't think that's what they are asking for. This is the same shit as when people were asking for a black character and we'd get comments like, ISN'T LUCIO ENOUGH? WELL WHAT IS REAPER THEN? Doesn't really help tbh...
Also, black women are the most mistreated and disrespected double minority here in the states (cannot speak worldwide but racism and colorism exists on all corners of the planet)... They get the worst of everything. So it's not a huge shock that people want that represented in a game like OW. Not lightly either, I want a character that leaves no room for ambiguity, especially with how big a deal colorism is.
I don't want a character people "think" is black. I want a female character that is undeniably/clearly black in the same way Brigette is undeniably white, Mei is undeniably Asian, and Orisa is undeniable 4-legged robot with an African accent. I would've said Symmetra is undeniably Indian, but somehow people still mistake her as Black.