So far, I have found conflicting answers to the question of whether the territories of the United States (currently all located on islands / groups thereof) are integral parts of the United States or distinct entities that, while possessions of the USA and not sovereign, are separate from the USA as such. To explain the difference, I will mention that while both the United Kingdom and France have overseas possessions, their legal relationship to these differs. Specifically:
-The 14 British Overseas Territories, which are the last remnants of the UK’s once far-reaching colonial empire, are legally not part of the UK. The UK is made up only of the territory of England, Wales, Scotland, and Northern Ireland and islands belonging directly to those four historic countries. Everything else is a possession. Places like Bermuda, the British Virgin Islands, the Falkland Islands, or Gibraltar are legally connected to the United Kingdom but are not integral parts thereof. There are also 3 groups of islands just off Great Britain: Gurnesey, Jersey and the Isle of Man, that are considered “Crown dependencies” but are distinct from the UK as such.
-On the other hand, France has 11 inhabited and 2 claimed uninhabited overseas territories. All these, while having different kinds of political organization and different levels of regional autonomy, are considered integral parts of the French state as per the 1958 Constitution of the 5th Republic, “Overseas France” being all territory outside Europe and the older European part being considered “Metropolitan France”.
How does the legal status of the US insular territories (which are, as I understand, up to 16 in number, three of these being contested and five of these actually inhabited) compare to this? I have been able to determine for certain only this: US territories are considered “incorporated” or “unincorporated”. In the former, the US constitution applies in full, whereas in the latter, it does not (or applies only partly). One explanation I’ve read is that incorporated territories (currently only one - Palmyra Atoll; it was once part of a larger incorporated territory with Hawaii and remained so after being severed from the latter after Hawaii gained statehood) are integral parts of the USA while unincorporated ones (currently all the others, including Puerto Rico) are just possessions. However, other sources claim that all these possessions are part of the USA. The law that governs who is entitled to American citizenship uses this definition of the United States: “The term “United States”, except as otherwise specifically herein provided, when used in a geographical sense, means the continental United States, Alaska, Hawaii, Puerto Rico, Guam, the Virgin Islands of the United States, and the Commonwealth of the Northern Mariana Islands.” However, this seems to be a definition used only for the purposes of the rules laid down by this law. Note that four of the inhabited territories are listed, but the citizens of American Samoa, the only other permanently inhabited American territory, are not automatically entitled to US citizenship even though they are considered US “nationals”.
Besides what I’ve already mentioned, is there any law or SCOTUS judgment that would determine more explicitly whether these territories are or are not part of the USA proper, or is this purely a matter of conjecture?
Also, much (most?) of the area of the 50 states was once made up of territories, e.g. Arizona, Alaska, Indian Territory, Oklahoma. Before these were given statehood, was there any doubt that they were anything but integral parts of the USA?