Why is a Mexican playing an iranian??

This movie shows how stupid the Iranian system is.

Every Iranian person has some sort of family there. This regime isn't
really fond of people exposing its stupidity, corruption and madness.

The whole movie is about a guy who did nothing wrong and is imprisoned
for 118 days because he had the guts to talk to an American comedian
playing "a spy".

This people are irrational monkeys. Jon probably had the safety of the
actors in mind. And Bernal brings the necessary star power to bring
the message of the movie across, which is a plus.

Do you know any Iranian actor with star power and no family ties
who can openly diss the governments stupidity in a movie?

There have been hundreds if not thousands of movies where a character is played by someone who in real life is not of that nationality. Hell, look at Daniel Day Lewis, playing Abraham Lincoln! He's not American, he's British! Yet he did an outstanding job! Casting directors choose the best actors they feel can capture the image of the character, and I'm sure Gael Garcia did just that.

Hes a great actor, it doesn't matter what he really is. These guys get paid to act, its not that difficult to comprehend.

Quote the raven nevermore

Most films need a 'name' to get made. How many reasonably known Iranian actors do you know? Apart from Omad Djalili, who would definitely be wrong for the part, I can think of none.

I don't know why we always ask that question, after nearly a century of movies where the ethnicity of the actor is almost always different from the character's. I think we tend to think that the casting of a film is something like armchair casting. Such as, when we think such-and-such actor would be perfect for a role, and we ask, why don't they cast him/her as said character? But we forget, or perhaps don't realize, that casting is not a like a buffet at an all-you-can-eat restaurant. When you make a movie, dozens of things are going to limit your casting choices. There are probably hundreds of Iranian actors in the world. But then, how many of them are in the age range for the character? How many of them can work in a American made film under the different regional film laws? How many of them are in a position where they can star in a film criticising their countries government without serious repercussions? How many of them showed up John's casting call? How many of them can, actually, act?

Making movies isn't a cherry picking situation. You don't get your pick of the litter, and even then, you have to make controversial choices sometimes. You make the best movie you can, with the resources you've got and your own best judgement. That means, sometimes the actors will be different ethnicities from their character. I get it. In the past, we used to do that for discriminatory reasons. But considering these days, where traditionally American icons are being cast from British, Israeli and otherwise non-American acting pools, we have to consider all those mitigating factors.

Speaking as a Persian/Iranian, I was pretty pleased with the casting choice. Gael Garcia Bernal looks Persian enough to me - so unlike the "Persians" casted in 300. That was absolutely ridiculous. People regularly mistake me for being Latina, and I don't really mind it. While there are obvious differences to you and me, I can see why someone would get the two confused strictly in terms of looks.

Why? The same reason they get nice guys to play villains, Army veterans to play Navy recruits, straight actors to portray gay people, living people to play dead people and humans to portray Vulcans. It's called Acting

It is called acting. People play people from different backgrounds all the time. Some do so better than others.