Why did I say I thought the USG was the prime mover of the WHO treaty/amendments?

Because the US proposed the IHR amendments from 12 months ago got the WHO process started. And read the below, from a White House fact sheet titled “Biden-⁠Harris Administration Announces Expansion of Global Health Security Partnerships and Releases Annual Progress Report from November 29, 2022:”

• Support the planned Global Health Security Coordinating Office being established by Republic of Korea and expected to launch in 2023, including strengthening coordination and collaboration with the U.S. Centers for Disease Control & Prevention’s new East Asia regional office.

BUILDING PREPAREDNESS AT HOME AND WITH OUR NEIGHBORS

While we build capacity globally, the United States will continue to invest in pandemic preparedness here at home and in our own region, working with partners in the Western Hemisphere.  The majority of our domestic goals and objectives are articulated within the recent National Biodefense Strategy and Implementation Plan.   Building on this Strategy, the United States will work regionally – in North and South America — this year – to build additional health security capacity. Specifically, the United States will:

• Commit, working with the World Health Organization and the Pan American Health Organization (PAHO), to initiate and conduct a renewed external evaluation of U.S. health security and pandemic preparedness capacity by the end of 2024, in line with strong U.S. commitment to the International Health Regulations and using the new Joint External Evaluation (JEE) 3.0 Tool…

• Establish and support, in collaboration with PAHO and the InterAmerican Development Bank, [These are the western hemisphere branches of the WHO and World Bank; interesting that was not mentioned] the Economic and Health Dialogue of the Americas (EHA), which aims to convene Ministries of Health, Finance, Economy, and Foreign Affairs of countries in the Western Hemisphere to jointly address the economic repercussions of COVID-19 and strengthen regional pandemic preparedness.

DELIVERING RESULTS FROM UNITED STATES INVESTMENTS
 
Investing billions of dollars today in global health security can save trillions of dollars and millions of lives. As requested in the Fiscal Year 2023 Budget, the Biden-Harris Administration urges Congress to fully meet this unique moment in history – by providing the additional resources needed to sustain and accelerate progress for these global health security partnerships, and solidify steadfast U.S. leadership in the Pandemic Fund.