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When David Cameron visits the United States this week, he will find a country whose national political argument has become more like our own in Britain than probably he – and certainly I – would ever have imagined. For America has learned, thanks to Barack Obama's crash course in European-style government, about the titanic force of class differences. The president's determination to transform the US into a social democracy, complete with a centrally run healthcare programme and a redistributive tax system, has collided rather magnificently with America's history as a nation of displaced people who were prepared to risk their futures on a bid to be free from the power of the state.

They are talking a lot about this in the US now. Suddenly the...