> All the 'large areas of land' that people want to live in already have dense cities.

If by people you mean 18th century farmers or 19th century merchants, sure. I guess you could make some semblance of an argument for countries like Belgium or Japan, but it's downright ridiculous to claim United States, one of the most sparsely populated developed nations, already has all the large cities it can support.

Increasing population merely to EU average would create housing for hundreds of millions.