The environmental controls you are talking about mostly protect the local environment. Protecting the local environment is great, but crudely speaking, the global climate doesn't much care about whether you dump some toxic waste in some part of China.
What I hear in complaints about the exports from the Americans is that they are worried about good old jobs for good old American boys and girls (preferably in a union that is a strong voting block one way or another). So I would take the Americans at their word here.
Yet again, if the local environment in China was a priority of the administration that outweighed concern about climate change, you would see a very different policy. Instead of just putting tariffs and other restrictions on imports of some Chinese goods. You can probably come up with your own examples.
