I'm not sure it's true that the Israeli government doesn't care about American public opinion, since they do benefit from American military support, but let's assume what you said is true.

Even if Americans protesting won't stop the genocide, won't end apartheid, I'd prefer that those atrocities are not committed with my tax dollars, with support from my government, in my name. The lesson learned from 9/11 shouldn't have been "we need to enact regime change anywhere in the world where American interest are opposed". It should have been "Americans better make sure they are OK with the things that their government is doing abroad".

I'm not OK with it, I'm not willing to risk dying in a terrorist attack so that Gaza can be levelled with "made in America" munitions. I'm not willing to risk dying in a terrorist attack so that oil companies and other big business interests have friendly regimes to collude with in the region as they scam the people out of their resources and freedoms.