USA-NATO: The Great Rift. Procedures, Scenarios, and the New Structure of European Defense

The debate on the U.S. commitment to the Atlantic Alliance has reached an unprecedented breaking point. After months of diplomatic tensions related to the Middle East crisis and the European refusal to militarily support operations in the Gulf, the hypothesis of a unilateral U.S. exit from NATO is no longer an academic abstraction but an operational scenario on which European commands are already working.

The Procedural Maze: Article 13 vs. Law of the Land

The exit of a member from NATO is regulated by Article 13 of the Washington Treaty. The international procedure is straightforward: a "notice of denunciation" deposited with the U.S. government (the treaty's depository) which becomes effective after one calendar year.

However, the real clash is internal to the USA. In 2023, Congress approved a clause in the National Defense Authorization Act (NDAA) that prohibits the President from withdrawing from the Alliance without a two-thirds majority in the Senate.

• The Yoo Doctrine: Legal scholars close to the Trump administration, like John Yoo, argue that such a law is unconstitutional, violating the Commander-in-Chief's prerogatives on foreign policy (Article II of the Constitution).
• The legal clash: An executive order of withdrawal would trigger an immediate conflict at the Supreme Court, with the risk of a "two-speed NATO" during the times of American justice.

The "Trigger" of the Crisis: The Mediterranean Fracture

Unlike in the past, the current crisis does not arise solely from "burden sharing" (the 2% of GDP), but from a strategic divergence on Iran. Europe's refusal to grant bases and airspace — with the emblematic cases of Sigonella in Italy, the Spanish bases, and British restrictions in Cyprus — has convinced Washington that the NATO architecture is now asymmetric: American protection for Europe, but no European reciprocity for the USA's global interests.

Geopolitical Consequences: A Power Vacuum

The U.S. exit would entail an immediate downsizing of the operational capabilities of the "Eastern Flank" and the "Southern Flank":

• Intelligence and Satellites: Europe would lose priority access to the U.S. surveillance and satellite signal network (ISR), the beating heart of defense against Russia.
• Nuclear Deterrence: The end of Nuclear Sharing (involving bases in Italy, Germany, and Belgium) would leave France as the only continental nuclear pillar, although Macron's Force de Frappe is sized for national interests and not for extended defense.
• Logistics: The ability for rapid projection to the Baltic States or Poland would be lost without the heavy transports and in-flight refueling of the US Air Force.

The New Structure: Towards the "European NATO"

The transition from a U.S.-led Alliance to a purely continental coalition would entail a radical reconfiguration of the command chain and strategic responsibilities. Here's how the structure of the "Euro-NATO" would change in its crucial nodes:

The Defense of the Eastern Flank: The protection of Poland and the Baltic States, today guaranteed by the rotational and permanent presence of U.S. brigades, would have to be entirely replaced by a Polish-German-led rapid reaction common Army. This would require a massive deployment of European ground forces on the eastern border to compensate for the withdrawal of the American conventional deterrent. For Italy, the U.S. exit would impose a drastic choice: doubling military spending to cover technological gaps or accelerated integration into the European Strategic Autonomy project. The centrality of the Mediterranean (the "Wider Mediterranean") would become a purely European responsibility, requiring the Navy to assume the role of lead nation in the southern basin, in coordination with France.

The Supreme Command (SACEUR): Historically, the position of Supreme Allied Commander Europe has always been held by a U.S. General or Admiral, guaranteeing the transatlantic link. In a post-USA structure, leadership would pass to a high-ranking French or German General, marking the transition of NATO under the political-military control of the continental axis.

Nuclear Deterrence: Currently, Europe relies on the massive U.S. nuclear Triad and the Nuclear Sharing program (which involves the use of B61 bombs stored in allied bases). Without Washington, the only pillar would become the extension of the French "Force de Frappe" to the entire allied territory, integrated by strategic coordination with British warheads, transforming Paris into the ultimate guarantor of continental security.

The Southern Command and the Mediterranean: The Joint Force Command (JFC) in Naples, currently U.S.-led, is the pivot of operations in the Mediterranean and North Africa. Its transformation would see a handover to the Italian Navy, in coordination with the United Kingdom, to ensure the continuity of surveillance and power projection missions in a basin that has become the exclusive responsibility of Europeans.

The announcement of NATO exercises without Washington in 2026 and Macron's offer for a European nuclear umbrella indicate that the "Plan B" is in an advanced drafting stage. NATO without the United States would be a poorer and militarily less intimidating organization, but it could paradoxically force Europe into the political maturity it has avoided for eighty years.