I wish to be very precise here on this extremely important matter. President Trump has not "decertified" the JCPOA Iran nuclear deal. Now Congress must ultimately be responsible. He has, after a lot of discussion and intervention by his national security team, failed to certify the deal. This is not something that was part of the deal, but an epiphenomenon put in place by the US Congrees as part of a deal agreed to by former President Obama to get the deal through, a matter of every 90 days the US president certifying that Iran is complying with the agreement. Two times running, President Trump certified it, confronted by the hard fact that Iran has been complying with the deal according to every official body in the world. But, he has said he would not certify it, and reportedly he has blown up over this matter with screaming fits his c. So his NatSec team has cooked up this partial save: OK, boy, fail to certify, putting it on Congress to really undo the deal.
In the face of way more to say than I shall here, let me point out odd items most will not. So one of those is a positive. Even if the Congress fails to do what is right and reasonable and keeps the deal going, probably Iran will not pursue an active nuclear weapons acquisition program. There are two reasons for this, which could easily be undone if Trump continues to insanely go after them.
The first is that this whole negotiation with Iran was an unnecessary farce to begin with. Vilayet-al-faqih Ayatollah Ali Khamenei was issuing fatwas against the building of nuclear weapons as far back as the G.W. Bush admin. Pres Bush even accepted two official National Intelligence Estimates (NIEs) that declared that Iran was not actively pursuing a nuclear weapons program. He did it twice. The fatwas by Khomeini were the ultimate reason why these hard fought and deeply studied NIEs came forth, representing after all a consensus of every one of 17 plus US intelligence agencies, who have a wide variety of perspectives, some of them almost insanely hawkish. But twice during the G.W. Bush presidency they came together to make this super official certification: Iran did not have an active nuclear weapons program, even though it had one earlier, one that dated back to the Eisenhower admin when the US supported their program under the Shah. But, the bottom line is that while Khamenei is alive, there will be no Iranian nuclear program.
What this means is that ultimately Obama's massive effort to negotiate a halt to the nonexistent Iranian nuclear program was ultimately a worthless empty exercise, much as I have on occasion praised it. I mean, it was a noble and heroic and difficult effort, Obama supported John Kerry in getting the Russians and the Chinese, as well as the EU and other obvious US allies, to go along with economic sanctions, which actually had an effect, given that Iran is actually a semi-democratic regime, so that even the hardliners associated with Khameini went along and agreed. And beyond Iran, it was a big deal, the UN officially supporting it along with the Russia, China, UK, France, Germany, and the UN Security Council (oh, sorry, a part of the UN), as well as most of the rest of the world, aside from a handful of countries (not to be listed, although in most cases their intel/militery support it).
The second is that even given this nonexistent fact that Iran was pursuing a nuclear weapons program, which all the US intel agencies said was the case, and Iran has been in full compliance with the JCPOA agreement as agreed by all observers, including even the senior US officials such as SecDef Mattis before a Congressional committee, Trumps and a few Israeli officials plus some from
Saudi Arabia and a few others,Iran has been in full compliance with the agreement. If Trump insists on ending the agreent, he will have only the support of Israel and Saudi Arabia and a few of its immediate neighbors.
Addendum: It would appear that to the extent Trump is even thinking, what he (and those in Israel and Saudi Arabia who support this nonsense) want is "regime change" in Iran. It is not good enough to have a relatively moderate Islamist government that obeys a treaty that limits its nuclear program, which was not directed at weapons in the first place anyway. In this regard they resemble the wildly messed up views of George W. Bush regarding both North Korea and Iraq.
I have posted here on this before, but it remains not widely known, that North Korea was not in violation of the nuclear agreement with it when the WBush admin went after them on the matter. Just as there is nothing in the JCPOA about missiles, there was nothing in the 1994 agreement about uranium enrichment, although most Americans believe the North Koreans were in violation of 1994 due to their enriching uranium. It was about plutonium, and they were following the agreement on that when WBush told South Korea's leader in March, 2001, to forget about the peace process, which Colin Powell supported, but the neocon hawks led by Cheney and Rumsfeld did not. They wanted to pull a Soviet Union a la Reagan and Bush Senior: regime change. That has not happened and now the North Koreans have nuclear weapons. Imitating this nonsense, Trump is in danger of getting the same outcome, although we can hope that Khameini keeps his fatwas in place at least for awhile.
As it is, while not pursuing a nuclear weapons program and opening to the world seems to be popular in Iran as expressed in their semi-free elections that reelected the government that negotiated the JCPOA, the "Green Movement" does support civilian nuclear power and also Iran maintaining a reasonably strong military to protect against unfriendly neighbors such as the Saudis, whose current leader has openly talked of war against and even in Iran. So, getting them to stop testing missiles and so on is not a likely outcome from any popularly elected government in Iran. If we brought back the Shah, well, maybe, but he is dead, and I doubt the Iranians would accept his son as a leader.
In Iraq, there was a majority ready to take over when semi-democracy was put in place after the US invaded under WBush and overthrew the Saddam dictatorship. Unfortunately, as the then Saudi leadership warned, who convinced Bush Sr. not to go all the way to Baghdad after throwing Saddam out of Kuwait, that majority is Shia and friendly to Iran. So, now Iraq is ruled by people friendly to our supposed super enemy, Iran, and their role in Iraq is one of those things that the Israelis and Saudis are unhappy about, along with their supposed role in Syria, Lebanon, Yemen, and some other places.
Bottom line is that if WBush had not dumped the Korean peace negotiations and invaded Iraq, our current president would probably be dealing with a less difficult situation in the Persian Gulf and maybe not even be facing a nuclear weapons armed North Korea. But our current president seems bent on doing his best to make sure that future presidents will have to deal with both a nuclear armed North Korea (no way they are giving those babies up, even if Kim Jong Un is overthrown) and a nuclear armed Iran, not to mention a world that simply mistrusts US leaders and has not interest in any diplomatic negotiations with the US about anything.