In an interview with Vice, President Obama proclaims he is embarrassed at the 47 GOP Senators who signed Arkansas Senator Tom Cotton's letter to Iran:
“I’m embarrassed for them. For them to address a letter to the ayatollah who they claim is our mortal enemy, and their basic argument to them is ‘don’t deal with our president ‘cause you can’t trust him to follow through on agreement.”
If anyone should be embarrassed it ought to be President Obama who has penned several letters to the Ayatollah Khamenei including one last November begging Iran to help the U.S. fight ISIS as well as to resume negotiations on a nuclear deal.
Apparently, in President Obama's mind, Congress is but his rubber stamp and not permitted to ratify treaties much less write letters to heads of state.