Um. Why exactly can't the MOU be killed? The strait is a powerful card, but as has already been exhaustively demonstrated it's not an automatic win button.
And to that, if the US exerted no influence then why did Israel sign an agreement at all? It's not like Israel has been pushed back with force; they've been making steady progress in consolidating their control over the yellow line towards the litani pretty much without pause. Without some degree of outside pressure, there's no reason for them to have stopped - much as they haven't stopped demolishing what little is left of palestine.