Simplify the following text for a Grade 19 native English-speaking person.
Original: Elizabeth II ( Elizabeth Alexandra Mary , born 21 April 1926 ) is the constitutional monarch of sixteen independent sovereign states known as the Commonwealth realms : the United Kingdom , Canada , Australia , New Zealand , Jamaica , Barbados , the Bahamas , Grenada , Papua New Guinea , the Solomon Islands , Tuvalu , Saint Lucia , Saint Vincent and the Grenadines , Belize , Antigua and Barbuda , and Saint Kitts and Nevis .
Simplified: Elizabeth II ( Elizabeth Alexandra Mary ; born 21 April 1926 ) is the Queen of sixteen countries in the world : the United Kingdom , Canada , Australia , New Zealand , Jamaica , Barbados , the Bahamas , Grenada , Papua New Guinea , the Solomon Islands , Tuvalu , Saint Lucia , Saint Vincent and the Grenadines , Antigua and Barbuda , Belize , and Saint Kitts and Nevis .