One could make a more compelling case for capital punishment. Beheadings in middle-eastern countries are looked down upon, assasinations being involved in Russian politics is often critizied and you can get executed for rather political actions in China.

By whom? Not by (the majority of) the Middle-Easterners, Russians, or Chinese.

However the face of the western world, US, has a death-row that is disproportionally black.

Disproportionate to what? Compared to the relevant crime statistics it's disproportionally white.