Transmission losses prevent most of what you are suggesting. Across a continent, even with high voltage low loss power lines, you lose 35% to resistance. This doesn’t count the added loss from stepping down the voltage at various substations and transformers along the way. You can expect another 8-15% more reduction from that.

You’re suggesting that the amount of excess power from one side of the country could be enough to power the other side (while still meeting the demands locally) with 40-55% losses. Come on.