Yeah, imagine if we could more or less losslessly transfer electricity over vast distances. Massive renewable energy farms could be built wherever there was sun/wind/rivers whether the energy consumers are close or not. Energy could be sent to pump water into reservoirs as huge centralized batteries. The problem with 'what happens when the sun isn't shining/the wind isn't blowing' could be sidestepped because it's always sunny/windy somewhere, so we just get the power from as far away as needed.
People seem to underestimate how efficient regular power lines are.
The continent-spanning european power grid has a total transmission loss of about 6% using 19th century technology (transformers and copper wires). Modern high voltage DC lines can perform even better. The main limitation seems to be that people don't want to have power lines in their back yard. Not something that superconductors are going to sove.
Also the cost of a equivalent superconductor network would be an order of magnitude more expensive that what is essentially room temperature metal cables with very basic technology - transformers, insulation, and switchgear.
A superconducting power network could be built today - it would consist of a pair of ceramic superconductors suspended in a liquid helium pipe, wrapped with 3 feet of insulation.
Every few kilometers, one would need liquid helium pumping and chilling plants.
Total helium losses to leakage wouldn't be too big. Electricity transmission efficiency would be reduced by all the chilling gear running, but still better than regular conductors.
The only real barrier is cost. Not even the cost of the superconducting material. You can't hang a 6 feet diameter pipe on pylons across the nation - you're going to have to bury it, and that's going to get exxxxxpensive fast!
I feel like this could almost be a slogan for the human race at this point. Our grasp of science and engineering has reached a level where's there's very few things we might want to build where we couldn't conceivably do it. We could build the most outlandish megastructures, infrastructure and space bases if we really had to, but it all just costs too much.
Interesting video on Chinese 'supergrid' from coal plants in the west, to the population centers in the east, a total length of 3,324 km (2,065 miles):
Increasing power transfer effectiveness by even 1% seems like it would be a huge improvement when you consider the energy demands of a continent. That's potentially a lot of CO2 saved.