Before revision: We aim to generalize the duality results of Bouchard and Nutz (2015) to the case of American options. By introducing an enlarged canonical space, we reformulate the superhedging problem for American options as a problem for European options .
After revision: We investigate pricing-hedging duality for American options in discrete time financial models where some assets are traded dynamically and others, e.g. a family of European options, only statically. In the first part of the paper we consider an abstract setting, which includes the classical case with a fixed reference probability measure as well as the robust framework with a non-dominated family of probability measures. Our first insight is that by considering a (universal) enlargement of the space, we reformulate the superhedging problem for American options as a problem for European options .