Those American states and cities which do take global warming seriously aren't going to stop doing so, and it's too early to say whether a decision like this will prove to be permanent, or merely temporary until someone else is in the White House. Or, you know, until Trump changes his shirt and his opinion tomorrow.

And internationally as well, I'm not sure it matters that much - Trump's America is a laughing stock already, which may not make much difference when it comes to its hard military and financial power, but certainly makes a difference in soft power terms. The US tuning out won't necessarily make other countries follow.