I've now played Italia I three times and I'm not sure the addition of the campaign submechanism is a Good Thing. It adds considerable complexity, with lots of opportunities for mistakes and misinterpretations as well as analysis paralysis.
Actually, I'd say that this is probably finest and most smooth flowing feature of the game. It seems quite intuitive and it feels correct enough in historical terms.
Of course successful campaign may change the face of the map entirely for a moment but that is one of the great things. Empires rise and fall. If game turn is assumed to be something along lines of 25 - 30 years each, a lot can and will happen.