It doesn't seem to occur to you that they are US legislators, who are there to vote for what is best for the US. If the US interests are not the same as those of Israel, they are morally bound to disregard Israel and vote for the US. If their religion prevents them from doing this, they have no business being in a US legislature.
Sen. Barbara Mikulski (D-MD) becomes 34th senator to endorse Iran nuclear deal (AP)
from the article: First thought on most Jewish Congress ever: Wow. Second thought: Oy