gavra-at-work: If Israel goes to war against the United States (declared or otherwise, enough if the US is support sanctions similar to those used against North Korea today or South Africa 30 years ago), it would probably lead to an awkward situation for most American Jews, but still wouldn’t lead to a holcaust. It might lead to most zionists being forced to move to Israel, but that’s all. Under American law as now understood, one couldn’t round up Muslim citizens (though aliens of a hostile country can be interned and deported). The only acts of genocide in American history (the “middle passage” and the Indian removals) were both illegal at the time, and did not involve systematic mass murder, and wouldn’t of happened with better communications.
If Israel and the United States ever find themselves at war, it would perhaps lead to expulsion and forced migration, not death camps.