I agree that the person who accomplished the change has talent & good photoshop knowledge. (I have mixed feelings about selecting our president as the subject.)
However, putting my personal feelings aside, I thought it might be interesting to speculate about the photoshop process.
FWIW: If I were to attempt the change, I would start with a selective color adjustment layer for changing the skin tones, as well as using curves & a photo filter. It seems that it would not be too difficult to find a photo on the net with the right hair style/color for cut & paste. Same for the eye color.
However, it might take time to tweak it all for the best effect. I doubt if I would be able to accomplish a satisfactory result, but it would be interesting to try some day. (Only for the experience with photoshop - not for any social reasons.) It would also be interesting to change caucasian skin to another skin tone, so on & so on. similar to the many morphing series of photos that have been published.
It would also be interesting to read the processes which others might try.