Well, I don't know. All the Senators did was to remind the Iranians (and the President, incidentally) that any deal that allows Iran to develop nuclear weapons will run aground in the Senate and not be ratified. Then all that will be left will be an Executive Agreement, which, if resorted to, can be overturned by the next President.
Congress is not intended to be bystanders in foreign policy. For example, in the 1790s, Congress passed a statute authorizing the President to have the Navy intercept neutral ships bound
for any French port. Capt.
George Little intercepted a Danish ship headed
from a French port. Capt. Little was sued for damages, and lost. The Supreme Court said Congress had the supremacy even over the orders of the President in his capacity as Commander-in-Chief of the Armed Forces. Little was liable for the damages to the Danish ship owner. That gives you an idea of how involved the Founders wanted Congress in foreign affairs.
As for Congress passing laws over the last few years, if the Democrats had just knuckled under and done whatever the Republicans wanted, there would have been lots of laws passed. The budget would have been passed on time, there would have been no shutdowns, everything would be peachy keen in Washington.
If only the Democrats had done whatever the Republicans wanted.