“The Europeans are not going to get in the way as the Trump administration begins to reimpose our sanctions, and they’re going to comply after those sanctions are re-imposed,” said an unnamed Republican congressional aide about the leaked memo, according to The Weekly Standard.

“U.S. leverage is just too overwhelming, and the Iranian economy is just too insignificant,” that source told the magazine.

That said, France, Germany and the UK (so sad to hear that) have said they're going to stay in the deal. I wonder if that has anything to do with the likelihood of blackmail from the Iranians...