USA doesn't collaborate with climate change

First of all, Donald Trump, as everyone knows, is the president of the United States of America unfortunately. Everyone knows that Trump is a machist, ignorant, racist, because he has kicked Obama out of the White House, and it is not the first time he has thrown out a black man from his house.
Donald Trump's government isn't one of the 190 pact signatories to try to curb climate change and reduce gas emissions that affect the environment.
And the question is: How can Trump be so ignorant? Because climate change is an important thing to keep in mind, but he ignores.
Everyone was pissed about this, what's more, the celebrities they rose up against him. Like Leonardo DiCaprio, in addition to be an actor, he collaborate with climate change. He became very angry with Trump and told him that it was a reckless decision not to sign the agreement.