We reconstruct the network of environmental policies diffusion across American states from 1974 to 2018. Our results highlight an inefficient structure, suggesting lags in policy spreading. We identify Minnesota, California and Florida to be the main "facilitators" of the dynamics. Targeting them ensures the maximum likelihood of policy diffusion across the country. We then evaluate the determinants of the inferred network. Our results emphasize the role of contiguity and wealth in policy transmission. We also find sustainable economic systems as well as state’s expected economic losses due to climate change as critical factors of environmental policy flows.