5280 feet per mile is >25,000,000 sq feet per sq mile. Texas is 268820 sq miles, add Oklahoma and call it 300k, times 25,000,000 is 7,500,000,000,000 sq feet.
That's 7.5 trillion, divide by 7.5 billion people, and get 1000 sq ft per person. 30x30 is 900 so everybody gets 30 feet by 30 feet.