Americans don't love the Iran deal. There is a lot they wish were different. But when they look at it closely, review hard-hitting critiques, and--perhaps most importantly--evaluate the alternatives, a clear majority recommends that their Members of Congress approve of the deal. Republicans do not concur, though they don't settle on an alternative.
The Iran deal will stand, at least until the next presidential election. Despite disapproval by a non-partisan majority of both houses of Congress, not to mention the American people, because of the incredibly low threshold to sustain a veto, not to mention White House arm-twisting and purely partisan support, the deal will stand.
Opponents to the Iran deal often say that they could have gotten a better deal. These critics are largely found in the U.S. and in Israel. Critics are right for scrutinizing any deal. They would not be doing their job if they were giving it an automatic pass. However, being critical because a better alternative is desired is not realistic.