> Your losses will be large

HVDC has been sending multiple GW at 3% loss per 1000km for decades.

> and a terrorist or adversarial attack would easily take out our overly concentrated grid.

What conceivable terrorist attack could put an appreciable dent in hundreds of square miles of solar panels or wind turbines spread out over hundreds of thousands of square miles of area, yet would not be much worse if targeted against a populated area?

By contrast, consider the Russian drone and missile attacks against Ukrainian power plants. Those same missiles and drones would destroy a few hundred solar panels or a few wind turbines, resulting in only a tiny fraction of their impact against thermal plants.

The large area taken up by wind and solar make them much less vulnerable to attack than traditional power plants.