Public diplomacy emphasizes the participation of state and non-state actors to achieve common goals. This article recognizes the participation of state and non-state actors engaged in shaping the political environment of a host country to advance common interests, with different levels of leadership. A model comprised of state and non-state actors implementing reactive, proactive and relationship-building strategies and instruments is proposed. In Mexico, regulations for genetically modified (GM) foods have moved from a restrictive to a liberal approach, and this change may be explained by analysing US public diplomacy efforts to promote ideas related to GM foods. This is an ‘intermestic’ issue with international and domestic actors involved. Applying the proposed model thus helps us to understand the strategies and instruments that state actors, such as the US executive agencies, and non-state actors, including MNCs and NGOs, implement to target Mexican stakeholders and generate policy change.