People have been migrating to cities for years and years now, the rural areas of America are less populated than ever. I'm sure there's some middle ground where we can put new power plants that are relatively unpopulated.
High voltage transmission lines are actually pretty efficient. We routinely distribute power over hundreds of kilometers. There are a couple that are over 2,000 km long, and numerous examples over 1,000 km.
Cooling water availability is a major factor in plant siting. So you're looking for unpopulated areas on coasts, lakes, or rivers, which is probably a smaller set.