...as for the JCPOA...it's the right thing to do, per the article's author's closing statements...
"Washington has tried hard to reassure the Saudis that they are not alone in their legitimate concerns about Iran’s terrorist activities and destabilizing subversion. President Obama has wisely sought to build confidence with the king and his young son. The Iran deal is a good one, and I’ve supported it from its inception.
But it has had consequences that are dangerous and alarming. In the end, Riyadh and Tehran are the only players who can deescalate the situation. The Saudis show no sign of interest in that road."
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While this is certainly a complex situation, the U.S. needs to act its part are the "Leader of the Free World" and ensure that Iran doesn't develop nuclear weapons...and not having IAEA nuclear experts on the ground in Iran won't get the job done...we need to walk and chew gum at the same time (i.e. deal with religious/sectarian issues between Saudi Arabia and Iran, too).
Link: https://www.brookings.edu/blog/markaz/2016/07/13/what-the-iran-deal-has-meant-for-saudi-arabia-and-regional-tensions/