“So what do you think happens in the U.S. if a judge’s “gag” order is breached by a journalist?”
Not much because in the US such orders are only lawful when applied to the participants in a specific case. They don’t apply to reporters at all.
There have been gag orders put on the media in the U.S. It is rare, very rare. The fact remains though that if a gag order is breached it is regarded as contempt of court. That is true here and in the U.K.
We are blessed to have 1st amendment protections here. The U.K. does not have that. So judges are probably not as constrained when it comes to issuing gag orders. In the U.K. true freedom of speech has been kicked to the curb some time ago. Thanks for that can go to LGBTQWTH groups.