[myrmidon]

I do agree that politics is a big enemy here (with nations historically being most willing to spend big on energy when reducing interdependence, like the french Messmer plan, instead of the reverse).

Honestly the "1m² around the world" is probably a pretty good proxy for what we would need to solve intermittency problems exclusively by boosting grid connectivity (instead of storage), rescaling this to 4m² cumulative cross-section could probably transport the total global electrical energy consumption over ~10000km (but the losses would get uncomfortably high from an economical point of view after crossing the 1000-2000km distance threshold, so you might want even more aluminium when you desire connections that long).

Btw: Underground cables instead of pylons are absolutely a nimby thing. Not only is it much more expensive, because you pay for the earthwork and additional insulator, but it also limits your voltage (to avoid overpaying for insulation even more).

Return current is typically free, either from balancing 3phase AC or because decent electrodes get you <1Ohm over any distance thanks to math for the DC case. Just talking high voltage here; for short range, lower power residential connections the situation is different.