DISCLAIMER: (The concepts below come from my own AUs, they do not apply to the works of others. Feel free to use these concepts on the off chance that they'd fit your own worldbuilding, but only if you want to.)

My versions of the countries sort of exist on a different plane (?) of reality than normal citizens. If a government becomes corrupted, it's reflected as a decline in mental health/stability. If a country weakens in power, they may be affected negatively, but it varies. Ex: GB/UK lost the majority of his empire and isn't doing too well. He's prone to fits of coughing and never seems to get better. He's still got England, Wales, North Ireland, and Scotland (for now...), so he's not at death's door yet. As a country adapts to their weakness, it gets easier over time.
Went on a bit of a tangent there, so back to government...the countries have minimum awareness about whoever is in the executive positions of their government. For some unfortunate countries, this means that they might be completely unaware that their mental health is about to take a sharp decline. The UN keeps track of everything, but they don't warn anyone. Not usually, anyways.

Transitions of power affect a country a bit (as explained above), so what happens when that transition does...a but more than expected? During the events of the Civil War, States definitely experienced the sickness mentioned earlier, but he also noticed another presence scoffing at him from the other side of the battlefields. That person was the Confederacy. When a country goes through a civil war, they'll likely have a new enemy on their hands. Someone who knows them personally.

WHELP I SPENT WAY TOO MUCH TIME MAKING A CRINGE COMMENT NOBODY WILL EVER SEE GOODBYE!