If you have just one country, you have to accept that there is big likelihood that it's going to be shitty. End of the day you have fallible people in charge.
If you have less cohesion among voters, then you have less cohesion among leaders. Which leads to corruption and cronyism, as every leader thinks "fuck this country, I have to secure the benefits of my voters and myself".
I seriously think smaller is better in every respect.