The Queen of England is a sovereign human entity. Only another sovereign human can file suit against another sovereign human being. When America broke its ties with England and made a Declaration of Independence, all Americans came to be on equal footing with the other King(s) (and Queens) of England, and the other countries. All Americans came to be Kings and Queens in their own rite. It has never happened before in the history of the world.
This is why Charlie Miller (and friends) have filed a Notice of Lis Pendens and addressed it to the Queen.