For whatever reason, the islands of the Lesser Antilles from OTL U.S. Virgin Islands to Aruba are all under American control. How will the U.S. group the islands into individual states?
An unlikely scenario but not completely impossible.
Most probable causes would be an early set of slave revolts against Britain and France which brought chaos for decades.
The early US would not have the navy to enforce control (or the political will). The southern states would not accept free Caribbean islands into the US. (unless there is some kind of MAJOR butterfly where slavery ends prematurely in the US). Perhaps after the American Civil War, the US start gobbling or buying up various islands looking for naval bases. By this point, the economic value of the islands were down and they weren't worth much.
France, Denmark and the Netherlands may conceivably sell. Perhaps Britain may offer their islands as a "trade" for some US asset (part of Canada captured in a theoretical war. Or the United States offers Hawaii, Samoa or some African territory if they get in the "Partition of Africa" in the 1870 timeframe. Colonial powers hate giving up a square inch of territory if only for pride purposes.
However, your question was regarding how any such theoretical state(s) would be divided.
I see language as the biggest stumbling block. On the French islands of Martinique and Guadeloupe, the population was large enough that they couldn't be simply converted to English on short notice. It would probably be at least two generations and I don't see them being given any form of rights until they spoke English. The Dutch and Danish islands were less populated and would pose less of a problem.
I think the Dutch Antilles (leeward antilles) were too far away to join any sort of unified state. Perhaps they would be like Guam, a protectorate.
The Virgin Islands, Guadeloupe, Martinique, Antigua, Barbados (if you count that) along with the lesser populated islands could form a state, maybe with Guadeloupe as the central capital.
Trinidad and the Leeward Antilles may be separate. Maybe Barbados.