The international relations of the wizarding world would be redrawn. Queen Elizabeth would use her diplomatic skills to strengthen ties with other wizarding countries. She might also introduce new trade policies. For example, trading magical artifacts for Muggle - made goods that could be useful in the wizarding world. The story could also explore how the wizarding world, under her rule, would interact with the Muggle world on a more regular basis. This could lead to some interesting plotlines, like how Muggles would react to the existence of a wizard - ruling queen and how the wizarding world would keep their secrets while still having a closer relationship with Muggles.
His life would change drastically. He'd be part of the royal family. He might have to attend many formal events instead of Quidditch matches. His friends from Hogwarts might not be able to visit him as easily. And he'd have to deal with the politics and gossip within the royal court.
A possible scenario is that Queen Elizabeth has a magical artifact that has been passed down through generations in the royal family. This artifact draws the attention of Harry Potter and his friends. They come to her palace to investigate, and she becomes involved in their adventures. She could offer them resources and protection in the Muggle world, while they introduce her to the wonders of the wizarding world.
Harry would likely be very curious about the court and its people. He might use his magic in small, discreet ways to amuse the courtiers, like making a flower bloom in his hand. He would probably be polite and respectful, but also a bit of an outsider. His different style of dress and his magic would make him stand out, and he'd have to explain himself carefully to avoid being seen as a threat.
She could completely transform the Ministry of Magic. Given her experience in governing, she might restructure it to be more efficient. For example, she could create new departments to deal with things like the proper handling of magical creatures in a more humane way. And in terms of the education system, she might introduce a more comprehensive curriculum that includes not only magic but also Muggle studies from a historical and cultural perspective.
The pure - blood families would be the most resistant. They would see Queen Elizabeth as an outsider and someone who doesn't understand the 'pure' wizarding ways. The Malfoys, for example, would try to undermine her at every turn. But the more progressive wizarding families, like the Weasleys, would welcome her. They would see her as a chance to break down the barriers between Muggles and wizards. And the students at Hogwarts would be divided at first, but as they see the positive changes she brings, more and more of them would support her.
It could be about Queen Elizabeth somehow being a part of the wizarding world in the 'Harry Potter' series. Maybe she's a secret witch or has some connection to Hogwarts.
In this fanfiction scenario, Harry Potter would likely experience a very different upbringing. He might be exposed to the high - society life of the British royalty. He could receive a top - notch education in a very formal and traditional setting, different from Hogwarts. Also, he may have to adapt to strict royal protocols while still having his magical abilities, which could lead to some interesting situations where he has to hide his magic from the public eye but still use it for good within the royal household.
The prophecy about Harry and Voldemort would take on a new meaning. If Merlin was in Harry, he might see the prophecy as just another part of the cycle of good vs. evil that he has already experienced in Camelot. He would approach the battle with Voldemort with a different strategy, perhaps using his knowledge of ancient magic to find a more permanent solution to the dark wizard threat.
One possible plot could be that Queen Elizabeth discovers she has magical powers and is secretly a part of the wizarding world. She decides to use her influence in the Muggle world and her new - found magical abilities to bring about a new era of cooperation between the two worlds. She could visit Hogwarts and offer her wisdom and resources to help improve the school, while also learning more about magic herself.
It might entail Queen Elizabeth as a character in the wizarding world. She could be a guest at Hogwarts, and all the students are curious about her. She might give a speech about leadership and how it's similar in the Muggle and wizarding worlds.