You have no idea of the amount of such cables that would be needed, nor than you have any idea of the difficulty of laying them. It is difficult in the same way sending rockets is difficult: we know how to do it and have been doing it routinely for decades, but that doesn't mean we could scale it to the point your project would need, very much like space colonization.
> We have 7000km gas pipelines. You think electrical cables would be more difficult or more resources?
Yes, because it's “lengths times number of cables” that poses problems. The amount of power you'd need to be able to transfer is beyond imagination! I leave next to a nuclear plant that produces a mere 3.6GW of power, and there are multiple high tension power lines going from there, and only up to a few hundred kilometers away: in your fantasy you'd need A THOUSAND TIME more (over thousands of time more kilometers). If you managed to send a spacecraft that's a thousand time bigger than ISS, that's already space colonization for you already. Turns out scaling this up a thousand time is far from straightforward.
> I think you over estimate how much land you need to power the whole world. There is plenty of space. Even on islands in the Pacific Ocean.
You are underestimating it vastly. The world consumes 30 PWh of electricity a year. At 30% of capacity factor (which is the best you can hope for, realistically only achievable in low-latitude deserts without clouds), and 300MW/km², you'd need 40 000 km²: that's the size of Switzerland worth of solar farm, good luck putting that on pacific Islands…
Orders of magnitude matter, and you definitely lack the sense of scale for these things. What you're talking about is science-fiction material.