The reason has nothing to do with "independence". It is that the US has the death penalty for this, and they want to kill people who commit war crimes.

At least that was the reason I was given in the US military. YMMV

I wouldn't believe anything the military tells you about justice.

The US military told people whatever they needed to tell them to follow orders. That's why they follow unlawful orders like those to extrajudicially blow up non-combatant US citizens abroad, and imprison people in Guantanamo for decades without trial, assist the disarming of innocent US citizens in NOLA in the aftermath of Katrina, blackball soldiers in Vietnam that reported war crimes, and all manner of other things that hardly anyone seems to be held to account for.

Nothing about the ICC stops the US from executing war criminals.

https://en.wikipedia.org/wiki/International_Criminal_Court

> The ICC is intended to complement, not replace, national judicial systems; it can exercise its jurisdiction only when national courts are unwilling or unable to prosecute criminals.

Has the US ever executed an American soldier war criminal?

https://en.wikipedia.org/wiki/John_E._Day

Interesting. Thanks for posting that. I hope the US will always prosecute war crimes of its own soldiers, but I'm skeptical--I don't think that's how war and power work.

Oh, I'm skeptical as well.

https://en.wikipedia.org/wiki/Eddie_Gallagher_(Navy_SEAL) is more the norm.

> It is that the US has the death penalty for this, and they want to kill people who commit war crimes.

> At least that was the reason I was given in the US military.

That's obviously nonsense. For many reasons:

(1) ICC jursidiction does not supercede national jurisdiction that is actually exercised—that's explicitly a basis for ICC jurisdiction not to be applied (it can be applied in the case of sham proceedings designed to provide cover). So it wouldn't stop the US from trying, and applying the death penalty to, any war criminals.

(2) The actual reasons for the the US opposition, including Congress passing a law threatening the ICC, are matters of public record, and are much more about the US wanting impunity for accused (American) war criminals than any fear of inadequate punishment.

(3) The US response to its own war criminals that it has had the opportunity to punish since the establishment of, and its refusal to join, the ICC has shown a singular lack of capital punishment. And even the occasional Presidential pardon after conviction.

Even for US military propaganda directed at is own personnel, that's pretty lazy, low-effort stuff.