Most science fiction authors (and historians) seem to subscribe to the butterfly effect theory of alternate history -- an incredibly tiny change in the past can have the most major of consequences in the future.
But some seem to see history as more of a matter of forces, momentum, inertia, etc. (think The Foundation series, where the Foundation couldn't stop things from happening, they could just make them less worse or shorter). You can change history in the short-term, but over the long-term it comes back to equilibrium because the forces at work are just too massive (sort of like dropping a stone in a lake -- lots of ripples at first, but eventually they die out).
Taking scenario in which Henry VIII gets a son and doesn't end up getting a divorce and leaving Catholicism -- what is the possibility that events would have unfolded in the same general direction anyway? For example, did the momentum of history mean that England -- an island nation -- would have had to take on Spain at some point because it (England) needed the New World in order to grow and prosper?
Similarly, as an island nation, didn't it have to embrace concepts of commerce, mercantilism, banking and reformation in order to survive and prosper?