Trump's de-certification is purely a matter of domestic law between Congress and the Exec branch. JCPOA is a treaty signed by the Senate. If the Senate reimpose sanctions as Trump wanted, it will have to renege on this international treaty under UN law. 

All facts confirm Iran have complied 100% with the treaty. Trump action is anti-fact, and based purely on his ideology of hatred, which applies to many things such as trade, climate change, foreign policy and human rights. It is indeed a historic tragedy that U.S. voters have put in place such a stupid man of primitive intelligence, extreme hubris. But a lot of the responsibility goes to Hillary and her party. 

The open question is whether the Senate will become a Trump too. Refute facts and revoke U.S. signature on the JCPOA treaty. If so, the country have achieved zero credibility in all matters of foreign relations.