Big copper cables have electrical resistance which results in line losses.
The line losses would be tremendous...most of the power would be lost to heat and RF emissions.
Can you prove that with math instead of just assuming abstract losses? How much real power line looses per 1000km for example? Soviet Union moved electricity around its vast spaces, using its non-high-tech united electric grid. Without any superconductors.
It is far more efficient to have highly distributed generation AND storage than to have an intercontinental power grid of supersized transmission lines.
Yes, it is. But it's much more expensive than global transmission grid.
Anyway, my point was not that we must concentrate on single solution, but rather that solutions exist in many ways, I just suggestged simpliest one (except that political fantasy part of couse).