If I remember correctly, the privatization of JNR was mostly political, and has little relation to the subsequent successes or failures of the railways. In other words, keeping it public would not necessarily have changed the outcome for passengers.
This tweet finds that US systems like BART and MTA have more employees, when adjusted by number of riders or miles of track, than JR East, which seems to contradict your comment.
If I remember correctly, the privatization of JNR was mostly political, and has little relation to the subsequent successes or failures of the railways. In other words, keeping it public would not necessarily have changed the outcome for passengers.