London exhibition puts US on show as postwar creative superpower

British Museum’s American Dream will touch on many of the themes in the turbulent presidential electionOn the eve of the most bitterly fought US presidential election in decades, the British Museum has unveiled a print created by Andy Warhol in 1972, a demonic Richard Nixon urging the viewer to vote for George McGovern – a spectacular and spectacularly unsuccessful campaign image that preceded a landslide victory for Nixon.Warhol used a bland official photograph of Nixon and his wife