Why the accents are English in the film - commercial choice

Take a look here. Nearly 3/4 of the movie's gross was outside the US. That's the main reason why the accents are the way they are.

http://www.boxofficemojo.com/movies/?id=princeofpersia.htm

American accents in this Middle East movie would have been groaned at among 3/4 of the audiences worldwide as they have been repeatedly for nearly 100 years. Especially irritating to those actually in the Middle East where this takes place.

Try watching something like this in a London theater; the first American accent that shows up, the crowd will react. Try watching Shakespeare in NYC for that matter; New Yorkers will rebel!

American actors go to London specifically to learn how to talk "like that". They are proud when they do it well and I think it amuses them. You can see several on the London stage at any one time.

Also some Brits are being played well by Americans on Broadway at any one time. The very funny Noises Off on now has a mainly American cast.

Some American tourists in some parts of the world try to sound British by the way so they dont get snatched.

***

However! Re the movie AMERICAN accents are said to be identical to what was spoken in Britain 2-300 years ago. Today's Queen's English (Gemma Artherton's normal accent, the one used in the movie) is in fact a newish "mongrel tongue".

Jake Gyllenhall is remarkably good at UK accents. He said he avoided certain parts until he learned. I saw him on Broadway with a thick British regional dialect that even British actors would have had to concentrate upon a lot.

http://deadline.com/2012/04/jake-gyllenhaal-makes-u-s-stage-debut-in-roundabouts-if-there-is-i-havent-found-it-yet-258633/

If this story took place more than 2-300 years ago... shouldn't Jake and Gemma have used that dialect? :-)