A couple of things:
The press release you sited from Boeing was 2012. It was public, not classified.
This is old technology in a big way. I’m VERY happy to see we’ve got something like this, and I suspect something like this was used by Israel against the Bushear nuclear facility a ways back.
I don’t want to know if there is a counter to this that we’ve got, or whether the Chinese/Russians have something similar/better than CHAMP.
There are non-nuclear, tactical EMP devices that use a conventional explosive to drive a magnetic armature to create a pulse in a low altitude deployment. Some were used in the activity over Kosovo during the Clinton years. The tactical stuff is very limited compared to a high altitude nuclear weapon tuned for maximum gamma production to enhance the Compton Effect. The latter is a wide area impact. The closest actual detonation with similar effects was Starfish Prime. I was living in Honolulu when that test occurred. My parents wouldn't let me stay up to watch the flash.