stopping pollution is not easy
can you think of a way to cut out every coal, gasoline, oil or other fossil fuel plant in the world and replace them with nuclear/solar power plants in less than a day? what about changing all gasoline/diesel powered cars? you'd need to replace them with electricity, solar power and so on, not to mention almost all trains, besides the electric ones. you'd also have to do this so fast that it does not stop trading or emergency services, which rely on electric life support and gasoline vehicles.
you'd also have the get not only the approval and backing of the united states, but the backing and approval of every country in the world. literally. every single independent state.