Jason Kelce Calls Dallas 'The Butthole & Armpit Of America', Mayor Responds

3:44 PM PT -- Kelce's remarks on the city of Dallas reached Mayor Eric L. Johnson, who told TMZ Sports he's laughin' it off.

"We have to consider that this may have been meant as a compliment from the guy who is most famous for leading the ‘Tush Push'," Mayor Johnson said.

"Or perhaps he has spent too much time at the bottom of piles to recognize a city on the rise. As we say here in Texas, bless his heart."

Jason Kelce's rivalry with the Cowboys is still going strong even in retirement ... check out the barb he threw Dallas' way Monday night -- it was so fierce, even his ESPN colleagues winced!!

The jab went down just before the Cowboys kicked off their "Monday Night Football" matchup with the Bengals ... as Kelce and the rest of the "Monday Night Countdown" crew were previewing the game live from AT&T Stadium.

Scott Van Pelt was attempting to switch segments from ESPN's "The Simpsons" coverage back to live action -- when he informed the audience of where they were located.

"This is the state of Texas," he said. "Arlington. Dallas."

Suddenly, Kelce interjected out of nowhere ... "Also, the butthole and armpit of America!"

Van Pelt, Ryan Clark and former Cowboys defensive lineman Marcus Spears quickly cringed at the comment -- and shouted at Kelce ... which caused the Eagles legend to immediately retract his words.

"I was joking!" he said. "It was a joke! It was a joke!"

All of the guys on set clearly understood Kelce was just messing around -- and rifting off a comment Mina Kimes had made just moments prior.

Still, the words likely won't endear Kelce to a Cowboys fan base that already loathed him following his 13-year career with the hated Eagles.

To make matters worse for Big D, the 'Boys ended up losing in heartbreaking fashion to Cincinnati, 27-20 ... making it a pretty rough Tuesday morning in the Lone Star State.