“stark difference in customer service” = Tipping works
,,, nah, I've met many great Americans in their non-work settings and they've been wonderful, welcoming people. When I get home I recall this aspect as much as the sights I've gone to the US to see. I've been to the US five times and it's a thing, for sure.
It isn’t tipping, it is the American personality, they are talking mostly about stores and the customers and clerks they run into in them, if you are pretending to be nice and helpful only for a tip, then you shouldn’t be in service work.