Seeing double (the population, that is)

[Byzantine Prince]

So NYC is self supporting and doesn't need to bring in water, food and electricity?

Texas needen't be self-supporting either. There is of course people that can stay back(or robots) that could bring in water and food and all else to the population in the hypothetical situation.

Of course it's pretty stupid to say that we all have to live in Texas, but we could definetly do with some more urbanization. After all civilizations always grew in the cities.

(dont tell me you dont find tribesman tasty )

Yes.

If that happens all hell break loose. It simple isn`t enough resources on this Earth to sustain that many humans.

That's somewhat true. The problem is in the distribution of the food and water. America produces enough surplus food to sustain Africa forever and Africa produces enough oil to pay for more food, but the problem is in the distribution of the wealth and the resources.