It saves lives -

After a bit of a blog issue, it is the US withdrawal from the Paris Accord. 

Arab Spring was related in part to energy price spikes that were a result of climate policy decisions that were not all that well thought out.  When a nation the size of the US or a confederation of nations like the EU make policy decisions that impact food and energy costs, the global ripple effect can be disastrous. The coup in Honduras was related to US efforts to get Honduras to increase palm oil plantation sizes and increase hydro-electric production. Bio-diesel tends to increase NOx emissions and policy that focus on CO2 instead of all emissions is creating air quality problems in several EU nations.

When you consider US states as independent states, the impact of policy is reduced while individual states pursue their own best environmental outcomes.  When the US sets policy the world tends adjust but when California sets policy, most of the world yawns.

The Trump election highlighted the Urban versus Rural divide in the US which should also highlight the different approaches available to Urban and Rural environmental policy.  Wood and biomass energy where there is low population density is viable, but in Urban areas, things like district heating and possibly cooling are a better approach.  Mass transit is only efficient when there are masses so that is not a Rural "solution."   All electric vehicles might solve issues in cities, but not where there might be a 50 mile commute just to visit a grocery.

Grow local, buy local, saves a great deal on transportation emissions which isn't much different than hire American, buy American.  In general, the "global" approach needs to die in favor of a local approach. 

North America produces about 7% of Mercury emissions, including natural emissions, while the majority is produce by "artisan" mining operations in third world countries.  Nearly half of "global" coal emissions are produced by third world residential and commercial use, and the impact of third world trash burning to salvage metals is a growing concern.

The world would benefit greatly from a return to standard clean air and water policy on a local scale with more nations and states minding their own business.