"If you're in America a lot it's easy to get into playing American. All of it, the sounds, the energies, all very different. But it's really hard to do the accent. I tend to try and stay in it all day, which is the only way I can manage it. It's worlds apart from what I grew up with." British actress Emily Blunt insists it's a struggle to pull off a convincing U.S. twang.