There's a McDonald's up in the town of St. Jean-sur-Richelieu, Quebec, just north of the border in upstate New York along the Richelieu River. I stopped there once and was amazed at how clean the place was. You could have eaten off the bathroom floor. Every time a table was vacated, two French-speaking girls came out from behind the counter and gave the table and floor around it a thorough cleaning.
I think it has more to do with the parents of the kids who are working there, and how they were raised. There are isolated spots on the PA turnpike where you see fresh, young helpful courteous folks working there.
Probably the nearer you are to a metro area, the more apathetic and surly the kids get.
SD