The U.S. hasn't declared war since WWII, so it looks like the entirety of the U.S. military is in violation of this. It's looking more and more like what actually gets prosecuted is a political decision.
Yes, this is true, but in a far more boring way than you imagine. Prosecutors have huge latitude on what to prosecute, and the police on what to direct investigatory resources to. At every point, the unconscious and sometimes conscious politics of the people making those decisions are in play. That’s what makes reforming the system so hard.