Regarding the preferences of the international market: I don't think they're primarily race-based. American films have dominated for decades because they're generally better-produced, better-shot, better-financed. To cite a historical example: in China in the 1920s, local filmmakers couldn't compete with Hollywood. But then talking pictures came in-- and in an age before dubbing, foreign films ceased to be easily translatable. There was a subsequent boom in Chinese silent film, lasting into the late 30s, but it had nothing to do with the complexion of the actors and everything to do with accessible product.
American films still have a reputation for delivering the highest-quality audiovisual experience. They don't have a lot of motivation to alter their casting methods.
Certainly part of Hollywood's success overseas has been the sheer quality of the film making (regardless of the quality of the scripts), but there is a strong belief among the studios that American films fronted by non-white actors and films that have a significant non-white cast do considerably less business overseas than those with white leads. This results in those films not getting international releases, or a select few getting very limited international releases. It also results in studios outright refusing to consider actors of color for lead roles in large releases, those big blockbusters that they are counting on to double or triple their box office take. Spike Lee, for one, has long argued against this traditional Hollywood thinking (and his Denzel-fronted flick, Inside Man, did over half its business internationally, proving his point). But to this day he can barely get his projects greenlit despite showing a film by a black director with a black lead could "travel" (despite his desire to make it, and despite its international profits, he still hasn't gotten a greenlight on a sequel to Inside Man, if you can believe it).
We agree that international audiences aren't swayed in a significant manner one way or the other by the ethnicity of the lead - a point I was making in my previous post if that wasn't clear. But I don't believe Hollywood isn't motivated to change their casting because they feel they're already making a satisfactory amount of money overseas. Their willingness to compromise in the face of pressure from the Chinese government being one example of them trying to squeeze a few more dollars out of an international market that is already providing lucrative; the fear that a film titled, simply, "Captain America" wouldn't fly overseas was another - it's why "The First Avenger" was globbed on, to pacify those they thought might be a little anti-American or, more specifically, anti-America being up its own ass; making GI Joe an international organization rather than sticking to its US-based roots was probably the most gratuitously pandering to perceived international sensibilities of any recent flicks. I also think they rely on a very specific formula that they believe appeals to international audiences, and part of that formula is a white lead (Prince of Persia and the Last Airbender being two examples of films that were seemingly whitewashed specifically to appeal to larger audiences).
If they thought casting an Arab man would have boosted PoP's take by any percentage, they would have done so. If they thought casting Idris Elba would boost sales for a James Bond movie, I'm pretty sure you would see that. In fact, they tried once before casting a black actress in a role because of her name: Halle Berry as Catwoman. After failing to land some high profile white actresses, they figured that Berry would bring in more dollars than an unknown white actress. Well, they didn't count on the movie being such a disaster - though it did bring in slightly more overseas than it did domestically so they couldn't put that one on international tastes. And I'm sure the lesson they took out of that wasn't "make a better movie" but rather "cast a big name white actress and it doesn't matter if your movie sucks."
One reason I'm a big fan of the Wachowskis is that they have shown themselves to be fearless when it comes to the ethnic makeup of their films. They tried to get Will Smith as their lead in The Matrix. Despite failing to do so, they still put together one of the most diverse casts for a blockbuster in recent memory, with a central role going to Laurence Fishburne and a future society that puts other sci-fi films to shame when it comes to diversity. And their latest release, Cloud Atlas, seems to include a very front and center romance between Tom Hanks and Halle Berry. But despite numerous examples to the contrary, Hollywood still acts as if non-white casting is box office suicide.