Valois Burgundy, King of France

Assume that Charles the Bold has a son instead of Mary.

And the line of the French kings die out in 1589.

And instead of the Bourbons, the Duke of Burgundy become king of France.

In this scenario, how strong is France? And what of the Habsburgs, who because of this scenario, don't possess the Netherlands, and Spain? After all, Philip the Handsome was the son of Mary of Burgundy, who in this TL, would be male. Let's assume that the Habsburgs still remain Emperor, and also king of Bohemia and Hungary.

What happens next? What would be the ambition of this mega-France, assuming that it holds together?
 
Assume that Charles the Bold has a son instead of Mary.

And the line of the French kings die out in 1589.

And instead of the Bourbons, the Duke of Burgundy become king of France.

In this scenario, how strong is France? And what of the Habsburgs, who because of this scenario, don't possess the Netherlands, and Spain?

There were good chances of the Spanish marriages regardless the Netherlands but they definitely don't get the Netherlands. Economically, France is much more stronger than Spanish/Imperial combination: usually, Charles V was running out of money before Francis I and that WITH the Netherlands. However, economic strength does not directly map into the military strength. Spain had a big pool of the infantry cadres and Empire was providing Charles with the landsknehts. OTOH, France still heavily relied upon the gendarmes (knights) and Swiss mercenaries (who did not quite grasp an idea of pike and shot formations). Then, of course, the fact that someone possessed the Netherlands did not automatically mean that he was able to tax them at will: all these territories had their "freedoms" limiting power of their sovereign. As a side thought, while both Charles V and Phillip II had noticeable problems with taxing the Netherlands, the rebellious provinces had been raising enough money to outspend Spain during the 80 years of war (while Spanish troops had been regularly underpaid, the Dutch had been famous for paying their mercenary armies on time while also building a powerful navy).

After all, Philip the Handsome was the son of Mary of Burgundy, who in this TL, would be male. Let's assume that the Habsburgs still remain Emperor, and also king of Bohemia and Hungary.

I'd keep Spain in the loop: even without the Netherlands the marriage was logical for both sides because it was balancing power of France. Then, both Bohemia and Hungary are an issue of the future: king of Bohemia and Hungary from who Hapsburgs inherited had been killed at Mohacs in 1526 and until the late XVII Hapsburg possessions in Hungary amounted to approximately 30% of the territory (at best).

What happens next? What would be the ambition of this mega-France, assuming that it holds together?

This depends on who is marrying whom and when. In OTL Charles VIII had a legitimate claim to the Naples (competing with the claim of Aragon) and Louis XII - to Milan (competing with the claim of Charles V). Would the Burgundian Valois have the same claims and would they press them if they did?

Other than that, probably the attempts to somehow undermine the power of Hapsburgs by supporting the Protestants in the HRE. A more ambitious program (like getting all territories on the left bank of the Rhine) could be an issue of a distant future (starting from mid-XVII). Which leaves Rousillon and colonial pursuits.
 
Burgundian Valois will likely have the claim on Naples (I am not sure about that) but not the one on Milan
 
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