Apart from keeping a weird election promise to the northern states I don't see the point in pulling out. Even fuel companies wanted him to stay in.
CA, NY and WA have already said they will just deal with climate change at state level, so it probably won't even change that much.
There's a lot of faux-outrage of "please won't someone think of the children" on social media though.
Do they know that the agreement does start for years?