The escalation of socio-economic and geopolitical tensions is heightening the potential for conflict not only in intercultural but also in monocultural communication. Within this context, the media plays a significant role in shaping public sentiment and fostering situations conducive to conflict. This study aims to define the Conflictogenicity Index of Media Discourse (CIMD), examine its correlation with national communicative styles, and analyse the specific realisation of Lexical Pragmatic Markers of Conflictogenicity (LPMCs) in contemporary Mexican and American media. A particular focus is placed on devising a methodology for calculating the CIMD and trialing it through the analysis of empirical data. The analysis draws on a corpus of 680 online publications from 2021 to 2025, sourced from outlets including La Jornada, Excélsior, El Milenio, Fox News, The New York Times, The New York Post, etc. These publications address the migration crisis − an issue of common concern to both Mexico and the United States − thereby framing the investigation of conflictogenicity within an “Us vs. Them” dynamic. The findings confirm that norms of national communicative style govern the selection, frequency, density, and permissible strength of negative evaluation in LPMCs. This study also reveals that both the perceived intensity of a conflictogenic marker and the overall CIMD are subject to cross-cultural variation. To illustrate, articles deemed highly conflictogenic within Mexican linguoculture may be rated as medium or even low on the CIMD scale compared to American media. Ultimately, the research demonstrates that LPMCs, as key indicators of conflictogenicity in discourse, not only signal underlying social tensions but also help to pinpoint the society’s most pressing issues.