"the Queen is not the head of the Church of England
No, she's the Supreme Governor. Is there a difference or is this just semantics?"
The head of all Christian churches is Christ (although the trinity of God the father, God the son, and the Holy Spirit is regarded as all a "three-in-one" entity)
In His physical absence, He put the governance of the early Roman Catholic Church onto his trusted disciple, Peter. Peter became in effect the first Pope and handed down authority to subsequent pontiffs. One of the Pope's names is "The Vicar of Christ" - vicar in its original meaning of susbstitute or stand-in, as in "A filmed car-chase is a vicarious thrill". The vicar of a parish was originally the stand-in for the rector, who was often a son of a local bigwig and too posh to take care of the parish himself.
As Christ's substitute, the pontiff can make all kinds of rules and regulations about worship and morals, and can (and does!) pontificate on matters concerning the personal and public behaviour of his flock.
Henry VIII removed his kingdom from the power of the Vatican, making himself the Supreme Governor. The Queen inherits that position, but she does not have, (or want, I am sure) any power over the ways that services in the Cof E are conducted, or what the congregation does in bed, or any of the Pope's almost supernatural-seeming powers. She is a kind of Chairman of the Board to the bishops and archbishops who run the organisation.