Re: @Def: clearly you have never read...
"what's stopping it from importing solar energy from southern Europe/north Africa, wind energy from Denmark, nuclear energy from France, or hydro energy from Norway?"
You can minimise them by moving to HVDC, but you still can't go much past 1,000,000 volts without getting all kinds of corona effects along the line. You can't make the lines heavier to carry more current as that means closer spaced towers and each tower is a leakage point for your power feed. You really don't want your corona to turn into an arc with DC because you have to shutdown the entire feed to stop it (DC arcs are self-sustaining)
Underwater cables are even worse and the largest undersea connectors anywhere are only about 2GW
As for north Africa: There's a shedload of potential demand building up in the countries where it would be generated and the inhabitants won't take kindly to "new colonialists" shipping it off for consumption elsewhere.