You obviously don’t understand the Corker bill. Obama was going to seal the deal as an agreement, which a President has the authority to make. The Corker bill made it law that Congress (Not just the Senate) had to approve the Iran deal for it to be valid. We could argue all day about whether it was actually an agreement or a treaty, but the reality was Obama was negotiating it as an agreement. Without Congressional approval, according to law (the Corker bill) the next President can nullify the deal.
Congress can impose it’s will on a President if Congress wants to. See Iran-Contra affair for a recent example.