Here's the result of some more modifications. A very minor tweak to "Captured governor_dialog.h" so that, when you choose the new government, the soon to be ex-governor says "Then
this town will belong to
the British." Or whichever nation. The point is, he used to say "Then town will belong to British."
And a lot more modification to "Enc_fort_dialog.c/h". It had no provision for America or Sweden, so options for both are added. Originally I was just going to tack a couple of lines onto the end of "Enc_fort_dialog.h", until I noticed that the French and Spanish lines have hard-coded king names which are either mildly incorrect ("Long live his Most Catholic Majesty Felipe, who will restore this town to the true belief..." - which Felipe?) or completely wrong (e.g. in "Golden Age of Piracy", the king of Spain is Carlos II). Replacing the name with a preprocessed variable set by 'GetNationRoyalByType' didn't work for a privateer with all nation choices as all the "Preprocessor_Add" commands were executed, the variable being finally set by the last one, which meant the option to install a French governor included the name of the king of Spain. So there was no choice but to split the lines, which meant a lot of "DLG_TEXT" lines needed their numbers changed, which meant the text lines for Sweden and America could go next to all the others. (In the process I found that one of the existing "DLG_TEXT" lines was wrongly numbered anyway.) The dialog also checks 'isEnabledTownCapture' so that you can't continue all the way to choosing a new governor if the town is protected by the storyline.
And then the French line didn't give the king's name at all. The reason is that "Periods.c" calls the Golden Age of Piracy French king "Louis XIV le Grand", but "period_strings.txt" calls him "Louis XIV le Grand
e". "Grand" (without "e") is correct, as he's a king, not a queen.

So "period_strings.txt" is now corrected.
We need some sound clips for American and Swedish governors. Especially American. If you want a laugh, start a FreePlay as an American, then go and talk to the nearest governor and listen to his voice greeting... Meanwhile, since "Enc_fort_dialog.c" wants to play a suitable voice clip for the new owner of the town, I compromised. If you hand it to America, it says "My factor will call upon your factor", while for Sweden it says "I'm not so much a governor as an agent of the monarchy" - suitably governorish lines which don't mention the wrong nation.