On the subject of a movement post-WWII to include all people subject to US rule as voting citizens via amendment to give non-states equivalent electoral status to state residents:
This was prompted by the suggestion of the USA obtaining Goa, which by the way remains very problematic but it might be fun to work it out. It would annoy the British but I think overall it would be papered over, because at the end of the day obtaining all three Portuguese south Asian holdings would not really upset the British system that much.
Post Civil War, Britain increasingly came around to the idea that the USA was too valuable a trading partner, investment opportunity and potential strategic ally to alienate too much. While I don't think it is very probable that a deal with Portugal can be made to happen at all, my notion is that it happens in the 1880s, particularly in the Harrison Administration. One President of the period who would want nothing to do with such a deal would be Grover Cleveland, who was anti-imperialist. But if Harrison could get it through the Republican controlled Senate of the day, Cleveland might find himself not much able to do anything about it.
Of the three possessions, Macao seems to be one that Portugal would hang on to through thick and thin. Just as well, since including Macao throws the whole timeline for a tizzy in 1949 and after...but in an optimistic version of the proposal, Truman gets the Amendment done well before then. If the USA has Macao on any terms, we are quite unlikely to fail to defend it, regardless of how it is administered. If we don't have it at all, then we can consider just the ATL mode of representation in isolation, since neither Timor nor Goa seem likely to seriously derail larger historical trends. The latter makes for some drama and tension with Britain for a time, but I think the isolation and peripheral nature of the holding, relative to large American concerns, would allow a modus viviendi to work out pretty soon and after that not much needs to change if that is what we want.
If we want major change as the point, Macao makes for it.
Anyway I mentioned a plan B--Truman's effort to get American non-state territory holdings regularized and settle the mess of the Insular Cases and so forth, for reasons of global US prestige and leadership mainly, and because of ideological notions connected to his New Deal common man mentality, fail. But the idea is put out there as part of the general Civil Rights era agenda. It sits as an idea stirring up some controversy through the 1950s, and then if we can assume a TL reasonably close to OTL, it gets swept up in the momentum of LBJ's Great Society in the mid-1960s. There are those who dislike that whole package, but there are few landslide elections in US history more trouncingly decisive than Johnson's win in 1964. This era gave rise to DC getting Presidential EV OTL, and I suggest that the Truman proposal gets the dust blown off it and takes the place of this. By then, Alaska and Hawaii will already have been admitted as regular states.
I therefore looked at the demographics. Now if the USA takes possession of all or some of the three Portuguese territories, that will change the demographics. On the whole I would expect some increase in population in Goa, due to Indians seeking to take refuge in US administration, despite some negatives, but part of the achievement of normalizing the mess that acquiring Goa would make with British relations is that the US policy would be somewhat exclusionary. World War II would change the rules. Timor will probably have a bigger population growth but it will be largely a backwater, especially after the USA acquires the Philippines, so no great drama, and its population would probably suffer at least as much if not more from the Japanese occupation. OTL the Japanese treated Macao rather carefully at least at the start, but the gloves will be off in the ATL if it is a US holding.
So my population estimates for all three are pretty wild guesswork, only somewhat guided by OTL populations which are rather vaguely counted themselves. However, all of them, even Timor the smallest, are quite substantial by standards of US states! Each is much smaller than Puerto Rico, but larger than many states. To my surprise, I find that if we control the increase in the size of Congress so as to maintain the same number of Representatives for the established states, 48 in 1940s using the 1940 Census, or 50 in the '60s using the 1960 Census, then actually in either case we'd add just 15 House seats in the '40s or 14 in the '60s. This includes DC, which by the way gets not one but two Representatives in either decade! It turns out that Puerto Rico remains about the same size as Oklahoma or Connecticut in both cases, and gets 6 Representatives, and the Portuguese legacy Commonwealths are also remarkably stable relative to the other states...Macao I am assuming has a smaller population than OTL, due to American policy preventing much of the immigration the Portuguese have permitted, because Macao is said to be the most densely populated place on Earth and I suspect American authorities would prefer to mitigate that a bit. Thus it winds up with only one House member in the 1960s, as its population is held stable at around half a million. But in the 1940s it would have two seats. Timor starts out in the 1940s being worthy of just one seat but with a higher population growth than OTL, due to a more benign and richer US presence probably including some active bases funneling money into the local economy, has at a guess some 850,000 people by 1960--it could be more since I didnt consider the actual military base populations! Assuming geo-politics like OTL there is some worry about Indonesian policy under Surkarno putting the possession in some jeopardy, but the coup of 1965 would banish these fears; Indonesia had good relations with the USA after that. As for Goa, I assumed pretty high growth there since the possession turns out to be much larger in area than I thought; I assumed it was just a city like Macao but it actually has a lot of hinterland. However it is still walled off from the rest of India by strong US borders, so I figured it would have reached a solid million in population by 1960, and that is probably a large underestimate. It too would be worthy of 2 House seats, more if it is much larger.
Overall then, we wind up with 15 or 14 more House seats, bearing in mind one more for the other Territories. And six more Senate bailwicks than OTL, bearing in mind I propose the Territories having one Senator only. Thus we wind up with 562 Presidential EV in 1940's, or 561 in the '60s, which is quite a modest increase over OTL's 538.
Given a very lopsided liberal mandate in the mid-60s, I think the Amendment could sail through then if not the 1940s. The three Portuguese legacy regions would become Commonwealths instead of states, on the Puerto Rican model albeit with representation in Congress and for Presidential elections PR does not enjoy yet OTL.
The hard and fast rule is, I think the USA would be reluctant to admit states in which the overwhelming majority of the population does not have English as their first language, though people in all four proposed Commonwealths would be fairly proficient in English as a second language. As Commonwealths they would be subject to stronger rule by Congress than states are, but on the other hand have considerable local autonomy too. Each is culturally unique and different from any other place in the American system.
If it is agreed Macao is too much of a wild card, and pointed out Macao is a territory Portugal administers to this very day, unlike Goa or Timor, and was profitable to Portugal, we can hew much closer to OTL in terms of global relationships and probable near identical geopolitical events. For that scenario, subtract one or two Congressmembers, and two more Senators and thus three or four EV for 558 altogether, just twenty more than OTL. Timor and Goa on the other hand I can see the Portuguese letting go, at least for a whole lot of money and other considerations. Either way, while all three are larger than I thought, they don't disturb the balances in Congress a whole lot.
