Henry VIII &Catherine of Aragon have a son, Catholic England

Pericles

Well there was an underlying Protestant movement and although it was being suppressed it might have emerged as a major factor later on. Especially since as Henry discovered with the dissolution of the monasteries there were economic as well as political advantages to the reformation for rulers. Unlikely to be in Henry's time as he had pretty much tied his colours to the Papal mast and with the marriage with Catherine being successful in producing an heir he's likely to retain the alliance with Spain. However 30 years down the line his son might think otherwise if circumstances change. For instance if Spain looks too powerful and dominant or tries to prevent other powers settling/trading in the Americas.

If England does stay Catholic that removes one of the problems with the Irish Pale and English control over the island, which will continue to receive Papal support. If Scotland still goes Protestant, which may be even more likely possibly with a Catholic England, that is likely to make relations between the two even more hostile. Doubt any Scottish Presbyterian king would be in a position to decide 'London is worth a mass' so even if blood links at some stage meant that a Scottish monarch was the direct heir to the English throne a union would be politically unacceptable to either or probably both sides.

A Catholic England that retains the Spanish link is possibly more likely to concentrate on traditional interests in Britain and France and might even see the Tudor's revive the Plangent claim, or at least 'regain' some of northern France. Spain might support some of this but is unlikely to welcome a English king in Paris as a unified state might challenge their power.

More likely France is going to be under pressure but likely to survive. You might even see, with it surrounded by Catholic enemies, the Huguenots come out in the civil wars and making France the leading Protestant power. Which could ally with assorted German rebels against the empire and possibly the Dutch presuming their rebellion still occurs. You could have some very big religious wars at least comparative to the OTL 30 Year's War.

Steve

  Lordroel

  No actually he seemed to get on very well with Catherine and they were married for ~20 years.  [actually about 15 before the messy divorce proceedings that took about 8 years thanks to papal opposition].  If they had had a surviving son then I doubt he would have broken with Rome and she seemed a very capable woman.  See her wiki entry en.wikipedia.org/wiki/Catherine_of_Aragon including the bits about her acting as Spanish ambassador and being Regent while Henry was in France.  Since she was 5 years older I could possibly see him taking mistresses later in life but, especially given her status as aunt to Charles V, emperor of both Spain and the HRE it would have been politically very difficult to divorce her without the sort of extended conflict that occurred OTL and I think is unlikely without Henry's frantic desire for a son.  Also Henry seems to have been a devout Catholic and only reluctantly broke with Rome.  The title the British monarch still uses today, 'Defender of the Faith' was actually given to Henry by the pope because of his early denouncement of the Protestants.

  Steve

Well, given his ego I would suspect the 1st son would be another Henry. [Actually checking the link for Catherine and her 6 pregnancies both of the sons who died shortly after birth were named Henry and given the title Duke of Cornwall]. Its possibly as likely that one of them survive as Mary simply being born a boy. A 2nd son might be named Arthur after his dead elder brother.

Not sure why his son by Jane Seymour was called Edward? Its an old regal name going back to before the Normans and hence the most commonly used of all but it was also the name of the main Yorkist claimants during the Wars of the Roses. Although since his father, after defeating Richard III married a wife from the Yorkish camp, it might be a choice for a later child but I doubt a 1st son would be called anything but Henry.