[Age of Reason]

Also, the United States has about twice the land area of the EU

Sure--we have so much land that every citizen can easily afford a few dozen acres overlooking the Atlantic or Pacific ocean.

Why, there's so much prime real estate in America, they're practically giving it away for free!

[Jedi Master Pikachu]

Many people can do without living near an ocean. To be fair, personally do live [relatively] close to one.

And the United States has one of the largest coastlines in the world (even excluding Alaska's).

But that coastline might not be so big if China or India (or some multi-national coalition) attack and the United States doesn't have the population to defend the nation.

Would you have the population wither to 100 million, or even 30 million as in Canada, or 20 million as in Australia? You'd have square miles and square miles of prime property then, but would be encouraging a takeover by a hostile, foreign power.

A large population is helpful not only economically, but also militarily. Ideally 100 million armed American citizens would be able to repel an invasion, but they'd still be weaker than 1.5 billion armed Americans.