That's a lovely bedtime story for children at Old Exeter, ending with a British strategic withdrawal rather than humiliating defeat, but we prefer to teach actual history on this side of the pond.
I think you're very confused about what sovereign immunity actually is. Sovereign immunity, also known as crown immunity, is the common law right of the monarch not to be sued, from which judicial and investigative immunity descend. My comment had nothing to do with the American Revolution, except to note that the British imposed this terrible concept across their now-defunct empire.
Willion v Berkley(1561) 1 Plowden 223, 75 ER 339 (K.B.), "[it is a] difficult argument to prove that a statute, which restrains men generally from doing wrong, leaves the King at liberty to do wrong" (Brown J), with Dyer CJ concurring.
Bracton, De legibus et consuetudinibus Angliae (c. 1235): "Quod Rex non debet esse sub homine, sed sub Deb et Lege".
Case of Ecclesiastical Persons (1601) decided in Parliament, "the king is bound by act of Parliament although he not be named in it, not bound by express words; and therefore all statutes which are made to suppress wrong, or to take away fraud, or to prevent the decay of religion, shall bind the King."
1615) 11 Co Rep 66, 72a, 77 ER 1235, Crown immunity from statute is confined to what in modern terms is the Queen's Consent and the Prince's Consent, and that there is no immunity from judicial review except with respect to the monarch personally (i.e., it is a personal protection rather than a corporate one).
Pawlett v Attorney-General (1688) Hardres 465; 145 ER 550, while consent of the monarch (sua sponte or under formal ministerial advice) is required for suits claiming money judgments against the monarch personally, equitable remedies against the Crown do not require consent.
Pawlett remained the law of England through the American Revolution.
Even though there has been statutory reform recently, this is still reflected in English law, and is one of the reasons why the recent headline constitutional case was listed as R. (Miller et al.) v the Secretary of State for Exiting the European Union.
Canadian law, incidentally, developed differently in the 19th century, and so it would have been listed as Miller et al. v The Queen of Canada.
Indeed the British badly mishandled the fighting in the American colonies, however that doesn't make your claims about the legal system of what was then Great Britain was correct, and your recent argument on that front is not supportable in English law of the time (and Scots constitutional law was not effectively in play during the American Revolution). Neither could whatever developed in the British empire after the Revolution was settled.
I think you're very confused about what sovereign immunity actually is. Sovereign immunity, also known as crown immunity, is the common law right of the monarch not to be sued, from which judicial and investigative immunity descend. My comment had nothing to do with the American Revolution, except to note that the British imposed this terrible concept across their now-defunct empire.