I posted the following in another forum :
Figured I'd try Russia. Hard, Domination, etc.
Goes great at first. Take all Ottoman Empire. Help Austria a little around Bavaria. Spain sends a 1/2 stack (really?) to Greece which I own.
After that mop-up I decide to cross Northern Italy to get M@rseille, and attack Spain and France from there. I take M@rseille, and liberate Catalonia. My long time ally and trade partner Great Britain decides "no more ally" and our points drop from +184 to +50. Why? No espionage, no borders shared (as if that should matter with +184), no turned-down alliance obligations.
Two turns later GB declares war on me. Seriously, this is broken. This happened in 2 back to back Russian Campaigns. The first time it was Austria with the DOW.
The only other thing besides it being broken is that it was on HARD? Even then, show a decline in relationship points first. It's like it was hard coded to do this.
Oh and ths has happened when playing as GB also on hard. Not sure if it ever happend on Normal.
Still, it's enough to make me not want to play NTW anymore, and I was liking most of it a lot.
So a guy answers that maybe it's due to me taking all those regions and perceived as too powerful so the other nations will do anything to maintain balance.
Has anyone ever heard this or have proof that this is a gameplay mechanic? I never have.
I answered this (just for reference):
With a +184? Then show it steadily dropping due to "Your Nation Too Powerful", or
something. I always monitor the relationships and watch my "Territorial Expansion" ratings.
Respecfully, I've never heard what you mentioned is a gameplay mechanic.