It surprise me that Poland is a not a member (ore was it not a real democracy in 1919) ore any South American countries.
Possibly because the creators of the idea wanted a combination of western democracies but not including states such as Poland that were stuck between Nazi Germany and Soviet Russia so securing that would require risking clashing with either/both of them so was considered too risky? It definitely wasn't a matter of democracy as the bulk of the population in the new federation would be colonial subjects of the assorted powers and I can't see many if any of them having any real rights. Depending on the date, especially if it was before Mar 39 then a possible additional member might be the rump Czech republic but again that would mean securing it against German aggression. [Guessing actually it is early in 39 as the map still shows the Bohemia region, presumably without the Sudatanland as still outside German control.
I think you might be right about Poland.
Found some nice things from the book who link you can read in the first post:
1. The legislative power of the Union is vested in the Congress, which shall consist of a House of Deputies and a Senate. Each shall choose its own officers, judge the elections, returns, and qualifications of its own members, determine its rules of procedure, have the power to punish its members for disorderly behavior, to compel their attendance, and to expel them by two-thirds majority; keep and publish a record of its proceedings, meet and vote in public except when two-thirds shall ask for a private meeting on a particular question, vote by roll call when one-fifth of the members ask this, form with a majority a quorum to do business though fewer may adjourn from day to day, act by majority except where otherwise stipulated in this Constitution.
2. The Congress shall meet at least once a year at a regular date it shall fix. During a session neither branch shall adjourn more than three days or to any other place without the other's consent.
3. Members of Congress shall not be questioned outside their branch of it for anything they said in it, nor shall they be arrested on any charge except treason, felony, or breach of the peace, during attendance at a session of Congress or while going to and from it.
4. No member of Congress shall hold other public office in the Union or in a state during his term, except in the Cabinet.
5. The Deputies shall be at least 25 years old, and shall be elected directly by the citizens every third year.
The number of Deputies from each state shall be determined according to population, a census being taken at least every ten years, and shall not exceed one for every 1,000,000 inhabitants or major fraction thereof, though each state shall have at least one.
6. Senators shall be at least 30 years old, shall have resided since at least 10 years in the State by which elected, and shall be elected at large from each state directly by the citizens every eight years, except that in the first election half the Senators of each state shall be elected for only four years. There shall be two Senators from each state of less than 25,000,000 population, and two more for each additional 25,000,000 population or major fraction thereof.
7. To begin with the apportionment of Deputies and Senators shall be:
Australia ..................... Deputies 7, Senators 2.
Norway ....................... Deputies 3, Senators 2.
Belgium ....................... Deputies 8, Senators 2 .
Sweden ....................... Deputies 6, Senators 2.
Canada ........................ Deputies 11,Senators 2.
Switzerland .................. Deputies 4, Senators 2.
Denmark ...................... Deputies 4, Senators 2.
Union of South Africa ........ Deputies 2, Senators 2.
Finland ....................... Deputies 4, Senators 2.
United Kingdom ............... Deputies 47, Senators 4.
France ........................ Deputies 42,Senators 4.
United States ................ Deputies 126, Senators 10.
Ireland ....................... Deputies 3,Senators 2.
Netherlands ................... Deputies 8, Senators 2.
New Zealand ................... Deputies 2, Senators 2.
Totals...................... Deputies 287, Senators 42.
8. To become law a bill must pass the House and the Senate and be approved and signed by a majority of the Board.* If a majority of the Board shall return the bill with its reasons for not signing it, the bill shall become law only if passed again by House and Senate by two-thirds roll-call majority and if a member of the Board shall ask to be heard by House or Senate during its debate thereon he shall be heard. A bill not returned by the Board within fifteen days (holidays and Sundays excepted) after presentation to it shall be law, as if signed, unless adjournment of Congress shall have prevented its return. This shall also apply to every order, resolution, or vote to which the concurrence of the House or Senate may be necessary, except on a question of adjournment, and to every expression of the Union's will, unless otherwise provided herein.
(* The executive, see Art. V. The United States Constitution gives to the President the powers this paragraph gives to the Board.)
9. The Congress shall have the power to declare war, make peace, and exercise all the other rights of the Union unless otherwise provided herein.
10. The Congress shall have the right to admit new states into this Union; but no new state shall be formed or erected within the jurisdiction of any other state nor any state be formed by the junction of two or more states or parts of states without the consent of the state or states concerned.