I believe near or at 90% of federal owned lands are west of the Mississippi, including a lot in Alaska, and in overall western states away from coastal areas. That's a pretty wide selection, but the best I can guess at this point.
And this exposes one of the critical flaws in this kind of centrally planned bullsh*t.
Settlements and cities emerge naturally at points where it makes economic sense for them to do so. That means reasons such as trade, access to navigable water, proximity to critical raw materials, etc..
That's a pretty good description of what most federally-owned land
isn't. So why in the hell would you want to build cities there? Who is going to move there, and why?
On top of that, It is inherent in Trump's plan that the
government is going to be selecting these particular sites, and that the
government is going to decide which of the proposed city models entered into this competition are the winners. What person who has ever voted Republican in their life actually believes that is a good idea?