How would that work with each stage? In America today you have cities, counties, state and finally the federal government.The old nation-states probably exist within United Earth the same way that Federation member worlds exist within the UFP.
If UE becomes basically the federal government, then nations are states, and states are counties, and on down.
Later you get the UFP as the federal government (?), entire planets/multiple planets/colonies are now single states, nations become counties, states are sub-counties, counties are sub-sub-counties, then cities.
But that assumes top down administration.
If existing nations remain essentially sovereign, then the UE isn't a federal government, it doesn't need to be one.
With the UFP (which Kirk calls an alliance) there's no effort to exercise top level authority, because there's no mandate. The members don't NEED the Federation to be a federal government, the members have that covered..
The Federation fulfills several important tasks, ultimate authority not being one of them.
001?Sector 000
USANorth America includes Canada.
Canada
Mexico
Guatemala
Belize
Honduras
El Salvador
Nicaragua
Costa Rica
Panama
Bahamas
Cuba
Jamaica
Haiti
Dominican Rep.
St. Kits and Nevis
Antigua and Barbuda
Dominica
Saint Lucia
Barbados
St. Vincent and the Grenadines
Grenada
Trinidad and Tobago]