It isn't legislation in the normal sense and the US cannot in any way 'authorize' Israel to do anything. It is a sovereign nation with full authority to make its own decisions.

The PROPOSED effort in Congress is merely a RESOLUTION that says the sense of Congress (or those there that agree with the resolution) is that such a strike would be in Israels' -- and possibly the US' -- interest. Perhaps. We don't know what it says and as it has little chance of passing and is merely political theater, I don't propose to waste time trying to find it and read it.

It's a dumb idea but that's what happens when you get 535 people under one roof -- a few are bound to be flaky. Make no mistake, that Resolution is flaky...