Gonna be honest, when I saw the US military two minutes into the first episode I noped out of there (I'm assuming you're talking about the falcon and winter soldier show). This was obviously going to be nothing more than a propaganda piece, and surprise surprise, it was. Reading an MCU wiki page on John Walker, I found a section mentioning he regretted some of the cruel actions he committed in Afghanistan but of course, let me guess (and I'm taking this guess without having even watched it): he didn't mean cruelty against civilians, he meant cruelty against enemy troops, or implied it (because if they don't mention civilians specifically, they expect you to infer it was against enemy troops (oh wait, I forgot, we're not supposed to call them troops, we're supposed to call them 'combatants')).

And this execution he committed, was it on foreign soil by any chance? I'm going to guess he did it in someone else's country.

It wouldn't be okay to take the law into your own hands here, but it's especially unacceptable to do so in someone else's country.