the The real question is, how would Sebastionano Sebastiano Di Ravello take over the usa USA? even Even with the help of the black hand. Black Hand, once di ravello Di Ravello even set a foot in the united states United States, he would have to use machine gunners and black hand titans even to counquer Black Hand Titans to even conquer a small city. i I bet he would be defeated immediatly immediately before he even got near a base. and the agency And The Agency and rico Rico would probaly probably have already killed di ravello Di Ravello
Even assuming that the Medici Armed Forces has been upscaled in the amount of infastructure, troops and vehicles and that somehow he managed to send such a force across thousands of kilometers for him to have somehow been able to conventionally take over the most powerful nation on Earth he wouldn't be able to deal with Mutually Assured Destruction but assuming that he doesn't bother trying to attack anyone else the world may just do nothing to him since the military he would have to have been able to take over the US would be so large that trying to fight it conventionally would be catastrophic as it would be to fight it with nukes since you'd also die so the world would probably end up having to suck up the massive damage done to the global economy due to them use pretty much being gone and move on while starting a massive build up on military forces and attempting to sabotage Di Ravello's regime and/or kill him.
And don't forget what Admiral Isoroku Yamamoto of the Imperial Japanese Navy said about the U.S. when he visited
"You cannot invade the mainland United States. There would be a rifle behind every blade of grass."
That's not the only problem it's also that Medici is far too small to have a military able to take on the US and that despite being an island nation in the mediterranean they have a major lack of a proper navy.
dont forget the black hand are also allied with The Agency so if Di Ravello had an alliance with the Black Hand which he does then he also has an alliance with the Agency plus the Black Hand have the Stingray base and the Eden ariship which the airship runs on bavarium and has a giant vacume capable of tearing up pretty much anything that gets in its path plus the attack drones and those turret tank things besides The Agency is also based in America so Di Ravello would have someone on the inside for informaton and The Agency posses high class weaponry which will be rvealed in the DLC so Di Ravello does have a chance.
Looks like in JC4, the Black Hand are allied with the Agency! Also, what would happen if the Black Hand attempted a U.S. invasion, remember they could have an Army the size of anything "technically", as we know they have soldiers across the globe.
Realistically, I'd have to assume that the Black Hand would have had maybe in the range of 200000 soldiers before Solís was captured. In that war they would have lost like... half of them. The rest would have been in other countries. But with out their homeland, it would make sense if each foreign unit (maybe up to 10000 each) either disbanded, or formed a smaller security company.
Having some treaty with the Agency doesn't make them allies. The highest Black Hand member is Gabriela, not Oscar. It was Oscar who had the treaty, so really the BH were never friends with the Agency. It's just reasonable to assume that during the treaty, Oscar and the Agency would have seen to it that they don't fight each-other anywhere.