I see your point. And in the context of your question, agree that the examples I gave are too basic to address the more subtle aspects of the issue.
It is an interesting issue. I consider the trend of casting roles more authentically in terms of the actor's cultural and ethnic background generally a positive thing (for actors and the audience). However I recognise that if the quest for ultimate authenticity overrides all other casting criteria, it can become counter-productive.
It is complicated. I don't recall anyone getting offended over Idris Elba and Dominic West playing American characters in The Wire. Many British actors work regularly in US roles, and do an excellent job of it. That said, I can imagine how the credibility of a show like The Sopranos would have been diminished if it had not drawn so heavily on Italian-American actors for its main cast.