US withdrawal from NATO faces significant legal and institutional barriers, including the 2023 Kaine-Rubio provision requiring congressional approval and recent bipartisan legislation like the NATO Shield Act introduced in September 2026 that would mandate prior consent and reporting. Tensions persist over defense spending disparities, selective alliance participation in operations such as those related to Iran, and US reviews of force posture in Europe, yet senior officials have stated there are no current plans for exit. No other member has advanced formal withdrawal steps, though isolated domestic proposals have surfaced in places like France. The North Atlantic Treaty permits exit only after one year's notice, and alliance commitments were reaffirmed at the July 2026 Ankara summit. Scheduled congressional reviews and defense posture assessments could influence near-term probabilities.