Quick Scoop

If the US left NATO, the alliance would lose its biggest military, intelligence, and logistical pillar, and Europe would likely have to move fast to build a more independent defense setup. It would also create a major legal and political fight inside the US, because Congress has already tried to block unilateral withdrawal.

What would change

  • Deterrence would weaken. NATO’s power comes partly from the certainty that the US is there; without that, Russia and other rivals could test the alliance more aggressively.
  • European defense costs would rise. Europe would need to spend much more on troops, weapons, intelligence, and command systems to replace what the US currently provides.
  • Ukraine would be hit hard. Reports say Ukraine depends heavily on US military aid, intelligence, logistics, and diplomatic backing, so a US exit would make Western support less coordinated and less effective.
  • US influence would shrink. Leaving NATO would likely reduce America’s leverage over European security decisions and could push some allies to hedge toward other powers.
  • US defense firms could lose business. If Europe retools away from US systems, companies tied to NATO rearmament could face lower demand.

Could a president do it alone?

Probably not easily. Several reports say a 2023 defense law bars unilateral withdrawal and requires either a two-thirds Senate vote or an act of Congress. Even if a formal exit were blocked, the White House could still weaken NATO in practice by reducing funding, skipping appointments, limiting intelligence sharing, or pulling officers out of NATO roles.

Bottom line

A US exit from NATO would be a major shock to European security and global politics, but the bigger short-term risk may be a partial US pullback that leaves NATO weaker without fully ending membership.