I recently became fascinated by the musical "Hamilton". I heard that it's mostly historically accurate, but there's something that doesn't sound right to me. In the musical, it is suggested that King George III threatened supporters of the revolution with corruption of blood and that Angelica Schuyler supported the revolution. Assuming that both statements are true, I cannot understand how could she be safe after travelling to London.
Why did George III not decide to revenge on her, given that she was already in his country?
To expand on my comment, the first thing to note is that George III was a constitutional monarch. He reigned but he did not rule. Parliament was the supreme authority in Great Britain.
'Corruption of blood' was an effect of 'attainder' under the common law in England and Wales. This could be the result of conviction in court (for high-treason, for example), or a Bill passed through Parliament. It was not something the monarch could simply choose to do.
Parliament had passed the Treason Act in 1777. This had been extended annually until 1783, but had been allowed to expire. Angelica Schuyler and her family didn't move to London until 1785.
In fact, those who actively supported the revolution were British subjects, and so by 'levying war against the king' they were probably guilty of treason under the laws of Great Britain [Bradley Chapin: The American Revolution as Lese Majesty]. However, I'm not aware that any were actually threatened with attainder.
After the war ended, American citizens were no longer subjects of the British crown, as expressed in Article 1 of the Treaty of Paris:
His Brittanic Majesty acknowledges the said United States, viz., New Hampshire, Massachusetts Bay, Rhode Island and Providence Plantations, Connecticut, New York, New Jersey, Pennsylvania, Maryland, Virginia, North Carolina, South Carolina and Georgia, to be free sovereign and independent states, that he treats with them as such, and for himself, his heirs, and successors, relinquishes all claims to the government, propriety, and territorial rights of the same and every part thereof.
Angelica Schuyler may well have supported the American Revolution, but she wasn't one of its leaders. What is more she was born in 1756, a time when women had relatively few rights under British law.
The war formally ended with the Treaty of Paris in 1783. Angelica moved to London with her family in 1785. Her husband, John Church had acted as a U.S. envoy to the French government from 1783 to 1785. He was a wealthy man when the couple moved to London, and within five years he had become a Member of Parliament.
Even had George III wished to seek revenge (something for which we have absolutely no evidence), there was practically no chance that she or her wealthy husband could be convicted of any offence in a British court that might also carry a sentence of attainder, and no chance at all that a Bill of Attainder would be passed through Parliament.
how could she be safe after travelling to London.
I believe this was a period when European nations did not much restrict the travel of their citizens, warfare was mostly conducted between armies & navies. Those civilians who could afford to travel were not necessarily treated as enemies or as combatants.
As Wikipedia reports:
After a brief visit to New York in 1785, the family sailed for England, taking up residence in London. Now the wife of a very wealthy man, Angelica entered a fashionable social circle that included the Prince of Wales (later King George IV), Whig party leader Charles James Fox, and playwright Richard Brinsley Sheridan. She also befriended and sponsored the émigré American painter John Trumbull, whose works included some of the most famous portraits of the American Revolutionary War era. Artists Richard and Maria Cosway also numbered among her close acquaintances in Europe.
Why did George III not decide to [take] revenge on her
I doubt he held her responsible for any personal injury. She was the wife of a British trader who became a member of parliament.
While Angelica was presumably a supporter of the revolution, she certainly wasn't one of its principals. Trying to blame a woman who wasn't plausibly its cause for the loss would have been extremely ungentlemanly by the standards of the time. It would also have drawn attention to the loss of the Revolutionary War, which would have made Britain look weak at a time when it was actually doing reasonably well.
Overall, seeking revenge on someone involved in the American Revolution almost a decade later would have made George III look petty and weak. This is a really bad idea for a constitutional monarch, and I doubt he ever considered it.
In Great Britain there was already a tradition of the loyal opposition, politicians not in power who hoped to win elections and replace the party in power with their own party entirely peacefully and legally.
So being opposed to the policies of the party currently in power was not exactly considered to be against the law.
William Pitt (1708-1778) The great prime minister who led Britain to victory in the French and Indian War or Seven Years War, opposed the policies of the British government in the American colonies and the war against them in the last years of his life.
It may be noted that all of the Hanoverian kings had bad relations with their fathers before them and with their sons and heirs after them. Every son and heir of a Hanoverian king formed an opposition group hoping to gain power when the old king died and the heir inherited the throne.
The only heir who was an exception was King George III, whose father Frederick Lewis, Prince of Wales died before his father King George II, and when the future George III was just a boy. King George III grew up to be devoted to his family and had a mostly happy family life.
George III's son George, Prince of Wales, the future George IV, was no exception to the rule, and supported the Whig party in opposition to the Tory party supported by his father. George III may have been angry at his son's opposition - including possibly opposition to the war in America - but he wasn't going to have his son and heir arrested for treason.
The Prince of Wales raised his daughter Princes Charlotte (1796-1817) as a Whig but that didn't affect the love between the king and his granddaughter.
After what was considered the decisive defeat at Yorktown in 1781 the independence of the USA was recognized by Britain in 1783. And in 1785 the first US ambassador to Britain was none other than John Adams himself.
It is said that when Adams was present to the King, George III said that he had been the last to consent to the separation of the colonies but was the first to wish for a friendly relationship with the new nation.
Considering that trade with the colonies had been an important sector of the British economy before the war, it was reasonable for the king to wish for a friendly relationship with the USA and the resumption of trade instead of stirring up trouble with the USA by, for example, having John Adams arrested for his previous acts of treason.
So if the king managed to restrain himself from arresting John Adams for treason, what satisfaction would he get from arresting little known supporters of the American Revolution? So if it was safe for John Adams to be in London in 1785, what would Angelica Schuyler, who I never heard of before today, have to fear?