What kind of cheese to use in baked spinach casserole?

If it is Italian-style, then Parmesan

If it is French or Swiss-style, then Gruyere or Emmenthaler (i.e. Swiss cheese)

If it if Greek-style, then Feta or kasseri

If it is Balkan-style, then kashkaval

If it is American-style, then white cheddar