BEIJING—For years, a wide spectrum of groups in the U.S. lectured, cajoled and entreated China to go green.

Multinationals and nonprofits teamed up with Chinese environmental groups to promote eco-friendly causes; Coca-Cola restored forests in the upper Yangtze. U.S. labs offered scientific support. Academics collaborated on research. The former Treasury secretary, Hank Paulson, championed China’s disappearing wetlands, a haven for migratory birds.

The...