One could make the opposing argument too, that Israel repeatedly inflames the region, engages in extra-judicial killing as a matter of policy, acts like a generally spoilt bully-boy - and all in the clear understanding that it won't have to pay any price whatsoever because America is there to protect it. Because the American political elite are a bought and paid for class of corrupt smooth talking crooks. The other opposing argument is that the world might easily be a far more peaceful place without America's constantly wrecking havoc and engaging in wars and military incursions and perpetual regime change in nations (HERE) that refuse to bend their knees to American pressure. I prefer that "other" argument quite a lot because I'm sick of American wars and regime change. They've been present throughout my whole life (and I'm an old guy now). It's not so hard as you're trying to make out. Under international law a war or military incursion has to be approved by the UN - or as in the case of Russia and Iran in Syria, invited in to the country by the mandated government of the sovereign state (Syria). What is clearly illegal is the USA's presence of military forces in Syria - uninvited and unapproved by the UN.