And yet, had all of the engineers in the US refused to participate in military work, guess who'd be running the world right now just the same? The world actually exists and the choices people make in it have real consequences. Not participating in military technology is an unbelievably childish option. If you are at all serious about the ethics of this, you have to choose to support the entity you trust the most. For me, that's the US. Feel free to make your own choices, though.