Marguerite Chapin was an American heiress who married an Italian prince and acted since the beginning of the XXth century to the Sixties her patronage on arts and literature. She published the review «Commerce» in Paris in the Twenties and «Botteghe oscure» in Rome after the Second Word War. Even if Marguerite Caetani has been studies from the view point of the history of literature, her biography presents various aspects which result of undoubted interest for historians. Her activity of publisher represented a cross-fertilization between American and European cultures. In this field Marguerite exerted a soft power whose importance increased after the Second Word War, when «Botteghe oscure» played a distinctive role in Usa public diplomacy. This paper aims to focus the cultural and political connections between the life of Marguerite Caetani and the history of the Twentieth century with the aid of Italian and American records neglected by the historiography on Marguerite Caetani.