Independent Protectorates:
My label of Independent Protectorats does not cover the lands of the Shire, the Treegarth of Orthanc, or the Drúadan Forestas. Though these lands have self governance they have closer ties depending on the Reunited Kingdom be it the place in the Reunited Kingdoms north council the Shire has or the protection of the enclaves under the crown, to the fact that they have to pass through the lands of the Crown if they wisho leave their lands. So herein this section i am to cover the Truly Independent Kingdoms of the Reunited Kingdom bar the vassal Kingdom of Rohan.
The first Independent Protectorate that is to be covered is the Kingdom of Dale in the north of Rhovanion. These lands are harder to define than any other I have searched so far for the Reunited Kingdom, there is little on the area of Rhovanion beyond the earlier days of the third age. To start on the defining of the Kingdom of Dale it is stated in the works of Tolkien, that Bard had rebuilt Dale and that the men from south and west had gathered to him and all the valley had become tilled again and rich, along with this the refounding of Lake Town. From this we get the post hobbit borders which many may recognize as a small circle in the north east of Middle Earth. However this is not where the borders of Dale end, long after this at the start of the Lord of the Rings it is said that the grandson of Bard now rules Dale and that his Realm now reaches far south and east of Esgaroth also known as Lake Town. The problem with this is it is not at this place stated how far is far in regards of south and east, for this I have two parts from Tolkien's works in defining the borders that you see on my map. One talks about the original founding of Dale around Erebor before it was destroyed by Smaug, Tolkien states that the Northmen who live between the Celduin (River Running) and the Carnen (Redwater) became strong and drove back the men of the east. The other part is during the war of the ring talking about the forces that threaten the borders of Dale, Tolkien talks about how a host of the allies of sauron crossed the river Carnen, and Brand was driven back to Dale (City not Kingdom). From these two parts we can well see that the Carnen is the eastern border of Dale during this time and during this time the men of the east occupied the lands south of Dale. The last notes on the lands of Dale that are made involve the men of the east being routed and fleeing back east to trouble Dale no more, there is no mention of Dale taking new lands and expanding its border from that of the pre war borders and thus I have not done this as well. This makes the west, south, and east borders pretty well defined, as for the north we know from Tolkien fell beneath Erebor and thus its North border would follow suit giving us its northern bounds from erebor across to the Grey mountains where the river Carnen is.
As for why I even included Dale in the Reunited kingdom and her map is because of what Tolkien wrote on Dale post war when he talks about the King in Dale and the King under the Mountain, sending their ambassadors to the crowning of King Elessar. After which he notes that their realms remained friends of Gondor and that they were Under the Crown and Protection of the King of the West. With them being under the King of the West they would fall under the Reunited Kingdom’s larger realm as the King of the West is the High King of the Reunited Kingdom. These regards also apply to the Kingdom of Erebor and the large realm of Durin’s folk as the King under the Mountain is also the King of Durin's folk and as Tolkien does not state Erebor as under the King of the West but rather the King under the Mountain and his Realm.
This brings us to the last protectorate, the Realm of Durin's Folk, this includes the Kingdom of Erebor, the Iron Hills, Thorin’s Hall, and the remaining dwarves in the Grey mountains. Erebor the first land of the dwarves in the Reunited Kingdom, its borders are straightforward as it is just the Lonely Mountain itself, marked on the map by Dale. Next we know that the Mountains of the Iron Hills, we know from Tolkien that many of Durin's Folk under the rule of d Dáin Ironfoot had dwelled in the hills. Though when he had become King under the Mountain it is likely many moved to Erebor but never stated that these lands were abandoned or lost by the Dwarves and this is the reason I still include them on this map. These are the same reasons for the inclusion of two other mountain homes of the dwarves, the next of which is Thorin’s hall in the Blue mountains. Its location and thus its borders are noted as the southernmost part of the Blue Mountains beyond the River Lune or Lhûn. With this as the location it is that I marked it and only the south part as other dwarves dwell higher. Though there are mountains remaining still south apart of the Blue Mountains they do not lie beyond the river that Tolkein mentions. It is also mentioned that many dwarves from these halls do move back to the Lonely Mountain; it is also never mentioned that they were abandoned. The last of the halls not fully abandoned is the Grey Mountains of which I have not marked the whole range. I have not included the whole range for two reasons one is the most of the Dwarves abandoned it as in the western parts dwell many Orcs from Gundabad, and then the lands north plagued the dwarfs with dragons, so of the Grey Mountains I have only marked the southern part for those that remained. For though Sauron was defeated Tolkien makes mention that not all dragons are gone and that the orcs, though weakened, still remain in the Grey Mountains. The last of the lands I mark as under the King under the Mountain is Moira as Tolkien notes that Durin VII retakes the halls some time after the year 171 in the Fourth Age.
The Kingdom of Dale and the Realm of Durin's Folk are the only independent realms bar that of Rohan, that Tolkien states as under the Crown and King of the West. This is why I have chosen to leave out realms such as the men and elves of the Greenwood and those that now dwell around the sea of Núrnen. It is likely that any other realms of the Free Peoples of Middle Earth and the freed slaves of Mordor are allies to the Reunited Kingdom but not directly under or apart of it.