Sure you don't have to have a single wire from one side of the planet to the other, but that's the point in a power grid. Even connecting two solar farms to the grid a time zone apart provides an extra hour of power to each of those time zones and reduces the risk of a single cloud bringing the country down
And as for the rest, you know what the electricity grid is right? Cables already run around the country, and if anything this reduces the strain on single connection as there are lots of smaller generators dotted around the country rather than a huge point of failure connected to a single power plant
On the contrary, Europe, Africa, Asia, the Americas are all wide enough that they can do plenty of solar trading during the daytime. Of course that does not provide energy in the night and that's OK.
Wind suffers the same problem as the sun in that sometimes there is no wind anyplace close, and it is even less predictable. While tide power is predictable and consistent, I don't live anywhere close to the ocean so we still need 2000km of wire to get it to me. Geothermo is useful when lava is close to the surface, but I don't live in such an area.
Note that my power is 80% wind, but it was done via several decades of building wind turbines, and I live in Des Moines which nobody would call a big city, if you live in a big city you have even more work to build it (you are both way behind us in building wind, and have a lot more to build)