With Saudi Arabia leaning increasingly towards BRICS and being more erratic in its support of the West, Israel is the last firm diplomatic beacon and region of influence the US has in the Middle East.
It also just so happens to be an apartheid state.
Even if public opinion sharply turned on Israel (it won't), the US would still hold firm in supporting it. Not because it's obligated to Israel or even because of sunk-cost fallacy. But because it would remove any chance of the US playing a part in regional hegemony.
I call it the 51st state because Israel's entire founding ideology is the same as the rest of the US - it's a white supremacist settler colony founded on ethnic cleansing of native populations, expropriation of lands from natives, and ethno-nationalism. It's part of the same ideological project and has all the same politics and all the same internal contradictions. American public opinion won't ever turn on Israel because they are American.