This goes all the way back to the beginning of the United States - the term "Christian Nationalist" is an efficient way of pointing out how divorced the modern Christian Right has become from the "founding ideals" that they claim to champion.
Not that you'd know that, given how you just shrugged and yawned it off.
NOW DEMS/LEFTISTS/LIBERALS ARE CALLING CHRISTIANS 'CHRISTIAN NATIONALISTS'. . . . . .AFTER 2000 YEARS OF BEING CALLED WORSE AND BEING PERSECUTED & MARTYRED IN THE MOST VIOLENT WAYS POSSIBLE 'CHRISTIAN NATIONALIST' FEELS ALMOST LIKE A COMPLIMENT.