I think you're giving the average American voter too much credit. First off, you wouldn't need 50%, just 50% of voters. More than half of the American voting population does not understand the conflict. Whether it's disinformation overload or apathy, too many voters simply do no have an opinion on what supporting Israel means. This is a nuanced conflict with a long history and complicated international implications. In the time it would take just to bring everyone up to speed, Israel could empty their arsenal of bombs.

Also, what makes you think the left is anti-war? For that matter, what makes you think there's a functioning left? We have two parties, and while they are not at all the same, neither of them is pro-Palestine. At best, you have political leaders who are anti-genocide, and very few are willing to call the Israeli response to Hamas a "genocide."

Now the right may be antisemitic, but they're also anti-Muslim. Really any target for hate will suffice, but currently it's the Islamic enemies they hate the most. Support for Israel is a proxy war against Islam, which is why you see strong support on the right. Israel can bomb all the civilians they want, and the military industrial complex gets to sell more weapons and vehicles. The Christian right would much rather see Jews and Muslims killing each other than have to get involved and do it themselves. Christian fundamentalists see support for Israel as good for America, because they can act like they are disappointed while watching two enemy religions try to wipe each other out.

I think if you put it to a popular vote, you'd see the public support Israel two to one. I don't have polling on that, I'm just guessing and could be way off.