Dumb Diplomacy: I think I may have discovered the solution.

[Slaists]

a few points: that 'friend-o-meter' is not how many + friendship points you get per turn but rather your current standing.

Playing Spain on VH I never canceled my alliance with France (rather joined them in all wars with joy) and still in 1745 they have neither canceled their alliance nor attacked me.

I find that 'random' declaration of war quite sensible actually. Things do go wrong in international relationships in unpredictable fashion (in real life). I feel, that programmer you're angry at has coded it quite well this time around (not in the previous TW series). I, for example, have not canceled my alliance with France and I suspect, France randomly declaring war on me is quite unlikely (but still possible) whereas your cancellation of the alliance might have just made the odds of such occurrence (DOW by France) a bit higher. It's not assured 100% that they will declare war on this turn or that, but they just might.

Also, notice that French public is not 'very friendly' to you but just 'friendly'. Something is brewing.

Imagine this situation: Shaking his wigged head, French King Louis is re-reading your alliance cancellation letter for the fourteenth time. In storms his remote cousing, Duke Pierre screaming and shouting about an arrogant Spaniard who just had seduced his daughter. "Oh, non... Your Daughter, Pierre!?? Oh, non.... A SPANIARD!???... Oh, non.... We MUST go to war this instant! Honor demands it!"... See, things happen...

When you pressed the re-load-the-turn button, a different reality took place. Pierre got a heart-attack from the news about his daughter; the French King just shoved your letter under his desk and life went on.