In my former government life I had a job that required me to talk with people from numerous countries and cultures from around the world. In order to be successful in that job I quickly had to learn that there was not a one size fits all type of approach to dealing with different cultures. You cannot talk to a person from France the same way you would talk to someone from Russia. A person from Thailand is going to see the world differently than a person from South Africa. I'm not going to get into the specifics of what the differences are because that is not the purpose of this post. I'm also not going to get into it because it is too easy to offend someone if I speak too generally, and that is the purpose of this post.
Too many times I see movies where you can tell the screenwriter did not really think anything beyond a character than "this guy will be Italian" or "this character is Japanese". The problem is then compounded when the director or actor decides that the best way to convey that is to just put on a fair to middling accent and call it a day "Hey mon, I'm Jamaican". A lot of this falls on the director and the actors, they are the ones who are ultimately in control of the characters. But the more work you do as a screenwriter the easier their job will be. You aren't allowed to get mad at the director and actors if you don't give them anything to work with. If you are the person who thought that some characters needed to be Jamaican and the only thing you did to characterize that is put "Hey Mon" in every other sentence then you didn't do your job.
It is not enough to simply know your character's backstory. If you are going to have a character from another culture you need to do your research on what that entails. Is it a culture that values honor? If so, what kind of honor? Honor for their elders? Honor for a sense of face? Are they an organized culture or are they a culture that has no concept of waiting in line? If it is the latter it is going to creep into their personality much more than just "Oh darn, that line for the movie is too long." They are going to appear rude and pushy to other cultures. They are going to appear loud and abrasive. I used to joke that when we dealt with someone from one of these cultures it was a recipe for disaster (I won't say which culture). People from this specific culture are used to pushing to the front and being abrupt with others they talk to and we (The Law Enforcement Personnel) are used to very orderly proceedings. The interactions were "interesting" to say the least, but the funny thing is that no one was being intentionally rude to the other. We were just acting in such a way our culture had raised us.
So I beg you. Do not just make a character be from a different culture just because you think it would be interesting. You owe it to the character, to the director and actors, to the audience and most importantly... to that culture to make sure you get it right.