As for why, well, precisely to avoid the bias at hand here. The tech, despite originating from the west, is what it is: a tech. Especially something as ubiquitous as Python, which is far from being scoped to the west.
We go to great lengths for equity in such boards, promoting openness and such: more women, more LGBT+, people of color, ... But even black people that are included are most often than not are afro-americans living in the west, and not africans living in africa. We always forget about foreign users that are also a minority, except a remote one we can shrug off, unless they are vocal enough.
That said, I acknowledge it may not be possible, the foundation likely being an US nonprofit, so integrating foreigners in the board may be extremely difficult.