In this chapter1 we reformulate and extend the analysis of small open economies of Asada et al. (2003a, chs. 8–10) toward some initial theoretical considerations and some numerical explorations of the case of two interacting large open economies like Euroland and the USA. However, we shall here reconsider the primarily simplified, compared to the 14-dimensional (14D) two-country Keynes–Metzler–Goodwin (KMG) dynamics of Asada et al. (2003a, ch. 10), only ten-dimensional (10D) open Keynes–Wicksell–Goodwin (KWG) growth and inflation dynamics.2 The results obtained in this chapter still represent work in progress and thus surely need extension in order to truly judge the potential of the proposed model type for a discussion of the international transmission of the business cycle through positive or negative phase synchronization and other important topics of the literature on coupled oscillators of economic origin.3