IMMIGRATION NATIONALISM, POLICY ESCALATION, AND DEMOGRAPHIC SPILLOVERS: NIGERIA'S EXPERIENCE UNDER UNITED STATES (U.S) RESTRICTIVE IMMIGRATION GOVERNANCE (2017–2025)

U.S immigration policy shifts have increasingly been framed as domestic political and security decisions, yet their effects extend beyond U.S. borders through “demographic spillovers” that shape population dynamics in migrant-sending societies. This article examines Nigeria’s experience under U.S. restrictive immigration governance between 2017 and 2025, focusing on migration-pattern disruptions, remittance-linked welfare vulnerabilities, and return and involuntary non-migration pressures. Drawing on a secondary-data-based descriptive-analytical design, the paper synthesizes evidence from international demographic and migration datasets and authoritative institutional reports, including United Nations Department of Economic and Social Affairs (UN DESA), the World Bank, International Organization for Migration (IOM), Department of Homeland Security (DHS) Office of Homeland Security Statistics, and major policy analyses. The article situates policy change within migration systems and demographic transition perspectives to explain how sustained restrictionism intensified by early 2025 policy actions and subsequent 2025 entry-restriction measures alters the predictability and accessibility of legal migration pathways, with downstream implications for household welfare and reintegration burdens in Nigeria. The findings suggest that persistent restrictionism corresponds with declining access to U.S. legal mobility channels, heightened migration uncertainty, increased non-migration/stalled mobility, and stronger reintegration pressure for returnees. While the paper does not claim causal inference, the patterns align with established evidence that restrictive destination-country regimes generate cumulative effects for sending-country demographic and welfare outcomes. The paper concludes with policy recommendations for migration-sensitive population planning, remittance-risk resilience, and reintegration support frameworks in Nigeria.