This NYT article on the nuclear deal and the Trump administration’s hostility to it gets to the heart of the matter here:

While Mr. Trump and his United Nations ambassador, Nikki R. Haley, have assailed Iran, they have presented nothing concrete that suggests the Iranians are violating the agreement [bold mine-DL].

Rather, they have objected to provisions that will expire after a number of years, called for more intrusive inspections even if there is no evidence of wrongdoing and say restrictions on Iran’s missiles should be part of the agreement.

To put it another way, the administration is desperate to find an excuse to get rid of the deal, but they aren’t finding one that anyone else takes seriously. They have no evidence the deal isn’t working because no such evidence exists, and so they are reduced to wishing that the deal included things that it doesn’t and probably never could include. The administration would like to change the terms of the agreement midway through, but that is both unnecessary and politically impossible. The administration is completely alone among the parties to the agreement in this:

The EU’s High Representative for Foreign Affairs and Security Policy, Federica Mogherini, insists that both Europe and the International Atomic Energy Agency agree Iran is sticking to the deal.

“There is no need to renegotiate part of the agreement because the agreement is concerning a nuclear programme, and as such, it’s delivering. We all agreed on the fact that there is no violation, that the nuclear programme-related aspects – which is all the agreement – are being fulfilled”, she insisted.

Despite the administration’s best efforts to change the subject or blame the deal for “failing” to do things it was never intended to address, no one else that matters thinks the nuclear deal needs to be “fixed” or ended. If Trump starts the process of reneging on U.S. commitments next month, none of the allies that helped us negotiate the deal will support him, and the U.S. will be the only one to blame if the deal subsequently unravels.