European leaders have made it clear they want the agreement with Iran to stay in place, because they believe it's working.
"This could become a real wedge issue dividing the other powers in the agreement ... against the U.S.," Sick said. "It could push the U.S. toward a decline in global power and U.S. credibility will take a huge hit, because we're basically telling the world the U.S. can't keep its word, putting us at odds with every other major power in the world, hurting our credibility, influence and reliability as an international partner — that's not a small issue."
Decertification could also hurt the United States when it's negotiating with other countries on entirely separately issues.
"Imagine trying to negotiate with North Korea when we just walked away from the most significant non-proliferation treaty in the history of the atomic age," Sick said.
O'Hanlon warned that the Trump administration is on a path that will force it to make "real decisions on Iran and North Korea that could make everything else this administration has decided on inconsequential."