It's completely meaningless because GWh aren't interchangeable. A hydro o thermal energy source too far from inhabited places could be used for bitcoin mining and its CO2 footprint would be near zero.
I'm not saying you are wrong but this requires a far more exhaustive analysis.
There are transmission losses, but they're not that great.
Please point out which power plants were built especially for proof of work mining. The others were apparently built with something else in mind and their power is now being wasted on western people's get-rich-quick schemes.
I'm not saying you are wrong but this requires a far more exhaustive analysis.