So the point is that accents can evolve naturally over a period if the person makes an attempt. Yes it gets harder as you get older. Just because someone sounds American-ish doesn't mean that they are not speaking it naturally.
A lot of people do not realize that their accent can actually be a hindrance in communication. They might have near perfect grammar but accents do cause a problem. I know this is a controversial topic and even pg got some flak for saying this but a "neutralized" (notice the American spelling) accent is important for communication. If you are a leader/CEO, even more important.
He still sounds Indian - eg 'more meaning', 'unbounded' has the emphasis on the vowels which is quite Indian. He also pronounces 'perseverance' differently from an American. I don't think he's putting anything on.
edit: why the down votes? Honest question, parent seems to be implying that its a bad thing that he adjusted to his environment, an environment where clear communication is paramount,.
Typically, it just requires spending time around the person and interacting with them. It doesn't matter where they are from or what sort of accent they have. After a few days, you'll understand them.
And also, an accent has no bearing on intelligence.
Out of curiosity, has anyone ever articulated why your Chinese is hard to understand? Is it tone or phonemes?
Do you mean Nadella's in particular? I didn't think it was that bad. Anyway it's only racist if you think less of a person just because you can't understand them. Remember there are lots of people who can't understand you, either.
Nadella shows no sign of this. He may not sound "perfectly american" but he's understandable enough for me. In fact, he sounds vaguely European. Keep in mind I am a Hungarian, born in Brazil who learned Hungarian, Portuguese and English in that order. If I can understand him, I suppose Americans will have little trouble ;-)