Who said I didn't use American cheese slices or Velveeta (which is another American processed cheese)? Velveeta and a can of Ro-Tel tomatoes with chilies, with a nob of butter and a splash of cream, makes a great queso dip - it doesn't seperate or get grainey. And the cheese slices - yep, can't beat the convenience.
I just hadn't seen the Velveeta slices ...