But if divided by population we are by far the dirtiest. Europe's problems have more to do with their labor laws than their environmental laws. The race to the bottom scenario you propose has some merit, but is not all it is cracked up to be. Companies are not quite that mobile because of the capital investments they have already made here. Additionally, there are major benefits to being located here, such as ease of distribution, the ability to more quickly react to market fluctuations, and an educated workforce.We are only the world's biggest polluter because our GDP dwarfs other countries. If divided up by GDP, we are one of the cleanest. All the regulations will do is push companies to relocate to countries with even lower standards than we have now. See what Europe is currently going through as a fine example.
Additionally, nothing said so far tends to rebut my general argument that we need to take the lead on environmental issues if we hope to be able to influence other countries to make changes. China's economy has been growing at a double digit pace and they are set to far surpass us in coal burning. They aren't using much in the way of "clean coal" technology either.