In an interview with The Sunday Times Blunt says she became a U.S. citizen for practical purposes.
It’s mainly for tax reasons. I didn’t want to renounce my Queen…The thing that’s weird is I do get to keep both my British citizenship and this, but you have to renounce her. So, it’s kind of typically American — not to be rude — but I had to renounce her in the room but I don’t actually, technically renounce her. They were like, ‘Just say it. You don’t have to mean it, but just say it.’..You have to learn all about the Constitution.You can’t be a habitual drunk, you can’t be on a guerrilla squad and you can’t be a prostitute, which is a shame.