think about it this way..
if we were mining using GPU's the electric used by the network would be much higher but the difficulty(security from brute forcing) would be weaker

that said
the total 23exahash is about 1.8mill S9 miners

however
there are half a million ATMS in america
there are 6700 banks in america, many bank call centres, head quarters
(1.4mill employee's probably with access to a pc each)
then we have the background stuff like visa, mastercard and amex servers

and thats before you equate the fuel consumption of the secure bank note armored delivery vehicles and staff getting to work
and thats before you equate the physical resource consumption of printing bank notes..

if you done some maths you would see moving fiat around uses more electric and is less secure than bitcoin

in short FIAT is less environmentally friendly