the whole "we gave them 400 billion dollars!" is one of my favorite low-IQ 'pub talking points. It was their money to begin with.
Oh, so you understand that but still claim that tax cuts for the wealthy are giving them money? <- probably a false equivalence but I couldn't help myself.
I am not terribly concerned that Iran will immediately do anything rash because then it would only prove Trump's point that they cant be trusted etc. So for optics sake they will hold off a little bit. This is honestly the same strategy Kim Jong Un is using - get sanctioned for being crap human being, threaten the world with nukes, have sanctions lifted.
I am probably most concerned that we are ostracizing ourselves from a broader group of allies that will exclude us from future decisions. But, I have always kinda thought "I sure wish the US didn't feel the need to be the world police" and this new brand of isolationism seems to assist that.