The other two are Venezuela and Syria - who didn't sign because they didn't think the accord was strong enough.
Secretary of State used to be quite the flash gig. Even unprincipled war-whores like Henry Kissinger and, well, most of them, got a bit of respect as they trotted around the globe reminding everyone that America was the boss, if only thanks to some glory reflected from their president.
Not much chance of that when you have to go out and front for a babbling man-child who makes the average reality TV contestant look stable. What can it be like having to make your mouth say plausible words out loud while your brain is wondering what your boss will have farted out in a tweet that directly contradicts them by the time you get back to your room?
Politics is to a large extent about the art of compromise, and few politicians have ever been more compromised than those surrounding the president of the United States. Tillerson is no exception.
In his time at Exxon he expressed support for a carbon tax and the company endorsed the Paris agreement.
Now he is twisting the truth to order. He backed Trump's decision to pull out by saying his actions reflected "the will of the American people".
Fake news, I'm afraid. According to a Washington Post and ABC poll, some 60 per cent of American voters opposed the move.
As for why Tillerson was here, it was "to reaffirm to everyone that the United States views this region of the world as being extremely important to both our national security interest and our own economic and prosperity interests".
So it's all about them, then. Anything else we can do to help, just let us know.
And yet - there were those protesters.
"I've never seen so many people flip the bird at an American motorcade as I saw today," said one US journalist accompanying Tillerson. What's notable about that is that he obviously has enough data to reach the conclusion.
Actually it was a paltry turnout. A tatterdemalion assemblage of a few windswept Wellingtonians and the usual failed Cirque du Soleil performers from Greenpeace shimmied up a crane to unveil a protest banner.
Even they looked dignified compared to the local politicians on the jaunt. There was a powhiri, lots of photo ops; everything to make Tillerson, a long-time associate of Vladimir Putin, feel at home, with the possible exception of vodka shots and Cossack dancing.
Sad.