1. US-backed Israeli expansionism and imperialism is the root cause of this conflict
2. Comparing Israeli war crimes and atrocities to those committed by the US for-profit war machine justifies neither.
3. Did anyone call the holocaust a 'holocaust' or genocide when it was just getting underway? Or do we have to wait until it hits some arbitrary numerical threshold or is complete before we're allowed to speak out?
4. Plenty of people accuse the US of genocide - just not the US media or brainwashed Americans.
5. As a US taxpayer, my money was not directly contributing to the slaughter of Chechnyans by Russia. In Israel, it is, and I am opposed to that, and so I speak out.
6. The US knowingly and willingly backed the Mujahedin and Islamic fundamentalists in Afghanistan against the Soviets - which then morphed into the Taliban. Yet again, Afghanistan (and the Taliban) is largely a mess US military adventurism created (and then couldn't undo after over 20 years of trying as you admitted). If anything, pointing out the ineffectiveness of the US slaughter of civilians in Afghanistan should be the argument AGAINST Israel resorting to these same idiotic and counter-productive 'scorched earth' tactics - not an example used to justify it.
6. Maybe the US taxpayer should push back harder on their imperialist government backing/funding and arming religious fanaticism, regardless of their professed religion or flag. This never ends well. Yes, the Israeli ruling class is full of religious fanatics too who express genocidal intent. The scary thing is, they actually possess the US-supplied weaponry to carry their desires out at an industrial-scale (as we are actively witnessing). This is all thanks to the hard work and labor that was skimmed from your paycheck and sent to Uncle Sam to ship more bombs to be dropped on Gaza. How does the aerial slaughter and starvation of poor Gazans by Israel benefit poor taxpayers in Ohio or Kentucky facing eviction or struggling to put food on their table too?
7. You're falling into the 'lesser evilism' trap, which I explain in more detail in my article:
https://medium.com/@pontifico/apologists-and-abolitionists-a74b847cce0a