That is only true if the Israelis are unable or unwilling to defend themselves (e.g. they do have weapons of mass destruction, don’t they).
Based on their public statements, neither Harris nor Trump would go to war to save Israel, even if it was being attacked by the combined forces of China, Russia and Iran. Trump believes in “America First” isolationism, and the Democrats are skeptical of Israel’s bona fides (and remember, the dominant wing of the party to which Harris and Walz are associated, are the ones demonstrating in favor of Hamas and its agenda).
While Trump might turn into an interventionist, “freedom agenda” Reaganite, and Harris might turn out to be just as pro-Israel as Biden, if not more (and have a John F. Kennedy like attitude towards to “axis” opposing American interests), if that doesn’t happen the Israelis need to rely of their own forces and military industrial complex if they want to survive (they also could rely on a Nes by doing tseuvah, but Israelis consider tseuvah a fate worse than be destroyed by the Arabs).