A reminder or primer to those discussing "law":
The leading current theories of law fall somewhere within the spectrum of "
Legal Positivism", whereby law arises from social fact, or in other words what people think and agree the law is. Be it Hobbes' theory of social contract, Kelsen's approach that there are basic norms from which, like in a constitution, all other norms follow, or HLA Hart's work which is more influential in the common-law / English-speaking world.
These theories mostly give little weight to enforcement or morality:
The law simply is what people think it is. And from this comes its authority: The USA surely excercises Molon labe - but not willy-nilly: They mostly restrain themselves by the law as US citizens may view it, who are at least vaguely aware of what the International Law established in the wake of the World Wars is, and how it is to no small degree an American creation. So in fact, US governments better adhere to those rules. That system of international law also had the recognition of a very significant part of the rest of the world, and generally states find it in their interest to act at least roughly or superficially in accordance with it, lest they get in conflict with other states or their own constituencies.
It is then mostly autocrats, who feel they are powerful enough to ignore and then shape internal opinions, who do what they can to also ignore what even they realise is international law.
I submit that a part even of the Russian population is aware of, and profoundly unhappy with, the fact that Russia is breaking international law.
And again, Russia does so in ways far more blatant than the USA does, even if the USA does it more often.