This study explores how Donald Trump’s political language operated as a tool of power in shaping international relations and diplomatic discourse during his presidency. Against the backdrop of a global rise in populist discourse, Trump’s rhetoric marked by an emphasis on national sovereignty, binary oppositions, and emotionally charged slogans offers a compelling case for linguistic and ideological scrutiny. Adopting a qualitative research design, the study employs Critical Discourse Analysis (CDA) to conduct a nuanced examination of selected texts: key political speeches and strategic public communications (including those delivered at the United Nations General Assembly, NATO Summits, the Presidential Inaugural Address, State of the Union addresses, press conferences, and relevant tweets). These data were chosen for their explicit focus on foreign policy, diplomatic themes, and the construction of American identity in global contexts. The analysis is grounded in Fairclough’s Three-Dimensional Model, which addresses the interaction between language (textual features), discursive practices (production and reception), and social practices (ideological and institutional context). To deepen the investigative lens, the study also integrates van Dijk’s socio-cognitive framework, which illuminates underlying mental models and group cognition, particularly in relation to populist “us vs. them” narratives. Findings reveal that Trump’s rhetoric consistently employs strong evaluative adjectives (“great”, “tremendous”, “strong”), modal markers of certainty (“we will”, “we must”), and binary pronoun constructions (“we” vs. “they”) to reinforce American exceptionalism and delineate adversarial identities. His speeches frequently adopted repetitive, conversational structures and intertextual references to past rhetorical frames, aligning with his “America First” agenda. These linguistic strategies disrupted conventional diplomatic norms replacing ambiguity with assertiveness and cooperation with confrontation resulting in strained alliances, heightened global polarization, and altered perceptions of U.S. leadership on the international stage. The significance of this research lies in its interdisciplinary contribution to English linguistics, political communication, and international relations. It demonstrates how linguistic analysis can reveal the ways discourse not only reflects but actively shapes foreign policy narratives. For researchers, the study offers a methodological blueprint for integrating CDA with socio-cognitive analysis in examining political rhetoric. For teachers and students of English linguistics, it presents a robust case study in applying discourse theory to real-world political texts, highlighting the tangible impact of lexical and structural choices on global diplomacy.