Is the US clinging onto "legacy tech" as old as coal? That's news to me, though I have to admit that I'm no expert when it comes to how our country is powered. I'd like to think the whole world has moved on from dirty fuel sources such as coal, since there are so many other options available.
Now, whether Trump's decision with respect to the Paris agreement could affect the global economy, that's anyone's guess. From reading that article and his statements, it would appear that this is a political decision made in an election year with no regard to the underlying issues--and that's a shame, but this is Trump we're talking about here.
I have got my fingers and toes crossed that he does not get reelected in November and that his replacement will at least attempt to undo some of the damage Trump has done to the country (and the world, for that matter).
I think Trump is a nationalist, not a globalist, so the issues of global warming, climate change, and other environmental issues that are usually raised by globalists do not attract Trump's attention. Like his former adviser, Steve Bannon, Trump is pro nuclear and fossil oil. For Trump, environmental issues are engineered by anti fossil oil and coal groups with the aim of harming the American economy. Although Steve Bannon has been dismissed as Trump's political adviser, his thoughts have deeply influenced Trump. This policy decision was made more because of the interests of the oligarchs who supported Trump and the republicans from the oil industry and arms contractors. In foreign policy, the United States continues to use the principle of control oil you control the nation.
America's exit from the Paris agreement opens up many opportunities for the leadership of other countries and the creation of new, more relevant decisions due to the absence of direct American interference in decision-making. But it also raises the possibility of a domino effect from this American attitude to other countries.