He does sound way too much like the 10th Doctor at times though.

Would have preferred him to do a different accent (not American).

maybe they thought he wouldnt be understood as a scot not us of course

I wouldn't describe it as a cameo, as the vast majority of the world's cinema goers probably wouldn't have a clue who she is. It looks to me like just a normal casting.
Cameos are usually reserved for big stars or actors who almost all the average audience are familiar with.