The original policy post is now missing from the whitehouse.gov site, but third party analysis https://www.csis.org/analysis/ai-diffusion-framework-securing-us-ai-leadership-while-preempting-strategic-drift says
Understanding the Tiered Framework
T1: The Inner Circle
T1 comprises 18 countries and reads like a roll call of long-standing allies:
Five Eyes intelligence partners (Australia, Canada, New Zealand, and the United Kingdom);
Close Western/NATO allies (Belgium, Denmark, Finland, France, Germany, Ireland, Italy, the Netherlands, Norway, Spain, Sweden, and the United Kingdom); or
Semiconductor heavyweights (Taiwan, the Netherlands, Japan, and South Korea).
But like all alliances, the omissions are as telling as the inclusions. Not all of “Old Europe” or NATO made the cut—Greece and Portugal are missing. More strikingly, Poland, Latvia, Estonia, and Lithuania are conspicuously absent, despite their vigorous support for U.S. security initiatives, especially in the wake of Russia’s invasion of Ukraine.
This partial listing underscores that unofficially, there is a secondary filter. It is not enough to be a stalwart ally on paper; to guarantee lockstep compliance, the United States wants partners whose re-export controls and enforcement frameworks mirror its own. For Washington, even otherwise-dependable allies may fall short if they lack the institutional capacity, enforcement rigor, and willingness to guarantee strict adherence, or if they are viewed as potential diversion risks.
T2: Eclectic Middle Ground
The lion’s share of nations fall into T2, a catch-all group that lumps together an eclectic mix of countries with vastly different levels of trust, capacity, and AI ambitions. India, Israel, Singapore, and Switzerland are placed alongside Yemen. There are several reasons why countries may have ended up in T2. Some, like Saudi Arabia and the UAE, have emerged as key investors in AI but remain outside the Western intelligence-sharing orbit. Others, such as India, are forging close strategic and trade ties with the United States but have a legacy of nonalignment. Switzerland, with its long-standing tradition of fierce neutrality, fits a similar mold. Meanwhile, countries in Southeast Asia and those in Eastern Europe that are officially close U.S. partners have been flagged as diversion risks.
T3: The Usual Suspects
T3 is a familiar roster of U.S. arms-embargoed countries—China, Iran, North Korea, and Russia, joined by the likes of Burma (Myanmar), Syria, and Venezuela.