If you actually want to make the United States mini, I would recommend first choosing a scale, then making the country with that universal scale in mind.
I can help in that regard!
Thing is, it would be far more massive and far more detailed than you are probably thinking the task will be.
For example, if we choose to make each flat 12 feet, that is, the approximate height of a floor in the Sears Tower (Oh, sorry, Willis Tower), that makes each brick 45 feet wide, meaning that the Sear's Tower would be 5 studs wide by 5 studs long. That would also mean that the contiguous United States would be in the range of 352,000 studs east to west, probably a little bit less, by approximately 190,000 studs north to south.
Also, where's Long Island? You can't have New York City without Brooklyn and Queens!