What a successful Armada of 1779 might look like.
-Although both sides see heavy losses, the Franco-Spanish alliance is able to annihilate most of the Royal Navy and launch tens of thousands of troops onto British soil, with a spectacular invasion of London seeing King George III slain and the remainder of the British government forced north. However, France and Spain don't have the muscle to impose their will on the British people, and a period of anarchy begins. With British loyalists drawn to the rapidly unfolding meat grinder in the UK, the colonists gain the upper hand in the American War of Independence and a sudden putsch overthrows British rule in Ireland as the isle is left undefended aside from Protestant militias in the north.
-"Once again, we bail you out of your stupidity": the Dutch attempt a second Glorious Revolution. They face resistance from loyalists to George III as well as the supporters of the late William Pitt the Elder, who was sympathetic to the American cause; these Pittite Militias are widely believed to be tied to France and to the Thirteen Colonies.
-Eventually the Dutch reach a deal with the Parliament (now based in Edinburgh) and force King George IV's regent and Parliament to reach peace with the US as well as with American sympathizers in the UK (the "Pittites"). The US gains independence as well as Nova Scotia and Quebec. The US and Pittites both eventually are convinced to muster troops to "defend the rights of Englishmen against Continental absolutism" in exchange for political concessions (reform of the House of Lords and the extension of a second Bill of Rights, including the freedom of religion, to all British and Irish citizens).
-By 1782, the situation on the British Isles has devolved into a stalemated war of attrition. The Anglo-Dutch alliance controls Scotland and around half of England, and Pittites and Yankees are gradually nibbling at London, Wales, and Ireland. However, the crown has had to make ever larger concessions to the Americans in order to keep them loyal, and the Prime Minister will admit that he has no control over what happens in Liverpool, much less the Pittite outposts in Dublin, Wexford, and Anglesey. At the same time, France has reinforced its position in the south of England and has been able to drive back almost every British attempt to retake the Irish heartland, and hordes of avowed "Papists" are weeks away from taking Dublin.