Metaphors are vital in political discourse, yet decoding their cross-cultural ideological nuances poses a massive challenge for advanced English as a Foreign Language (EFL) learners. This quasi-experimental study evaluated the efficacy of Metaphor-Mapping strategies explicitly charting source-to-target domain mappings on the retention and application of intercultural political vocabulary. Sixty Vietnamese university English majors were divided into experimental and control cohorts for a six-week intervention. Quantitative data from pretests, posttests, and delayed posttests revealed that the experimental group achieved statistically superior gains (p < .001, d = 2.59) and exhibited minimal semantic decay over time. Qualitative interviews confirmed that visual mapping minimized communication anxiety and enhanced learning self-efficacy. The study underscores integrating cognitive linguistics into advanced vocabulary pedagogy to foster intercultural communication readiness.