Will the US ever "fill up" to old-world population densities?

[recycled]

Originally Posted by fagrance

North and South America are the only places on the planet with vast green areas that are largely empty. South America especially is very underpopulated.

This omits one of the largest sparsely populated green areas on the plant - Siberia covers 13 million sq kilometers and has a population density of 3 people per sq kilometer. Few other places on earth have that low density.

[Vacanegro]

North America was on of the last contents to be settled - unlike India, China, and the Middle East, yet we now have the third largest population. We are already dense by Americas standards.