NPCs in the first MP1 became superpowers because espionage in that game was hilariously ridiculous. They would build a huge spy force, utterly destroy a country several times over, and use all the stolen wealth to further enlarge that spy force. This vicious cycle made it nearly impossible to top them.
To protect against just that, even with the nerfed espionage rules, I made it so they do not commit black ops unless they've been given good reason to. Indeed. Spies are safest kept at home, since sending them abroad stretches your resources. (This is another reason to employ one of the three NGOs to do your dirty work; yes, I'm using this post to advertise Ailedhood, Celticfury, and Filli Noctus' services)
Currently the most dangerous NPC would be Catalonia, but they're subservient to the GCI barring anything extreme.
When the insurrections occur next turn, Catalonia will become a GCI territory (as Sonereal prescribes), and government Victoria shall be in Katter hands.
There shall thus be only 3 true major NPCs: Louisiana, which is a staunch isolationist and is content to play the lyre while Rome burns; Prussia, a pragmatic, but regionalist, power; and Bengal, a country not too eager to get into a brawl, but standing to advance the cause of human rights around the globe (as Dem Taqat was before his departure).
The MP1 NPCs' main advantage was they knew the mechanics well enough to make the best course of action, which was the very imbalanced espionage. To unbalance espionage at this point in the game would require ENORMOUS sums of cash, that no single player has. It was also possible, due to the way teching in MP was, to neglect certain areas of spending once enough money was in it, due to the sheer size of technologies involved. But now, since every unit if gold can alter the balance of power, it is near suicidal to completely neglect one's army or espionage in favor of economy, or vice versa.