I was curious because of Adelaide Kane, who was Tenaya-7 in Power Rangers RPM, so I checked out a few minutes during commercials on White Collar. But Kane is much more engaging as a villain than a protagonist, it seems, for she was rather dull in most of what I saw. And the Australian Kane didn't seem to handle an English accent as well as she handles an American one. Not to mention -- why were a Scottish princess and a French prince both speaking with English accents?
Scottish queen, you mean. Mary was Scotland's queen from six days after her birth. James V died right after she was born.
I suspect the thinking on the part of the producers is that in costume dramas everyone speaks with an English accent. In reality, Mary had a flawless French accent; she was raised in Scotland by her French mother until she was five, and then she was raised in France after that. She would have been about fifteen, and Francis about fourteen, at the time of this episode.
There's a lot of accent fakery going on in this beyond Adelaide Kane. Megan Follows is Canadian and best known to viewers my age as Anne of Green Gables.