I have no proof that it was "bad"
According to the head of the CIA and now Secretary of State we have no proof that Iran has violated the agreement
Does backing out make us more safe or less safe?
Does backing out help with our credibility in futures negotiations with any country on any subject?
Chuck Schumer had a great analysis of the deal from 2015 I believe, and I tend to agree with him, that it was a bad deal. I'm glad we backed out.
The Paris Climate Accord was terrible for us as well, having us subsidize undeveloped countries which was just essentially a bribe to have them skip fossil fuels. Both deals needed renegotiation. I'm not saying the idea and spirit behind them was flawed, but those deals themselves were bad for USA. If you're a globalist I could see how you could agree with them, but I am not and thus think since they were bad for us, they needed to be redone.