Italian beef has always been a normal thing growing up in Norther IL. I was about and hour south of Chicago. When my nieces were born starting in 2000 I'd go down to Indy and they didn't know what Italian beef was doing there. In 2016 a timberframe crew came up from South Carolina and they didn't know what Italian beef was. Many in Indy now know as Portillo's had opened up a couple restaurants here and it's a main staple there, and they are very popular. At home it's easy to make:
I throw 4 lbs of beef chuck roast in the crock pot, 2 cans of Campbell's Beef Consume, one packet of Lipton Onion soup dry mix, and several table spoons of dry Italian herbs(sage, rosemary, and thyme and sometimes can have other things too). Let it go low and slow and in 3-5 hours the beef should fall apart easily and your place will smell wonderful. Put the beef on small french rolls.
Good accompanying things are cooked green bell peppers slices, Mozzarella, Pepperoncini peppers(spicy buy not hot).
I think portillos slices the beef very thin and then cooks it versus leaving it whole like I do in the crock pot. If you have a different recipe for Italian beef, post it here. Always looking for ways to kick things up a notch!