Well many of the countries where the war crimes happened are signatories to the ICC, so that isn't gonna be the problem you think it is.
Also: the US acting as a rouge state is not a power move it is a sign of moral decay, corruption and a critical failure to uphold the principles laid out in its own (wonderfully written!) Declaration of Independence.
It is just sad to see how hollowed out these great ideals have become.
Prefacing that I disagree heavily with the US actions under this admin and a lot with previous admins.
These ideals were always hollow. There is no law between sovereign entities, only martial might and political game theory tactics. It’s why the EU struggles so heavily with tighter integration. None of those sovereign states who are members want to give up the ability to do what they want and be subordinate to another power.