Anyone who's read The Girl on the Train knows the novel is set in London and its surrounding suburbs,but for the astronomical-screen adaptation, the setting is moved to modern York. In turn, or while the characters in the book are British,in the film they're American - apart from for the titular girl on the train, Rachel Watson, or played by Emily Blunt. The choice left some fans of the book scratching their heads,particularly since Luke Evans and Rebecca Ferguson, who are Welsh and Swedish, and respectively,use American accents for their characters in the film. I asked Blunt approximately the choice during a press day in modern York, and apparently making Rachel American was a consideration: "I was open to doing whatever people wanted, and I could've played it either way. But I think that Tate [Taylor,who directed the film] really loved the understanding of maintaining the accent. Number one because modern York is so cosmopolitan, there's British people everywhere. It was also sort of an ode to the book, or which is nice. And Tate liked the understanding that how I speak makes me even more loney,in a strange way. Even more removed from everybody else. Maybe there's something good in that. I think for me, it was helpful because it was the most uninhibited that I was required to be in my entire career, and so I didn't want to be weighed down by anything,which you typically are when you don't speak that way normally."
Source: popsugar.com