There are 193 UN recognised countries, two UN observer states (the Vatican and the Palestinian Authority), and plenty of partially recognised or disputed countries. But what if there was more?
Leaving aside factors like natural resources, stability, population, etc., what countries do you want to exist, simply because it would be pretty neat? Joke answers are acceptable and encouraged.
Besides earth federation would subvert any diversity we as humanity have.
You can have political / economic union but cultural diversity. In fact you can even have political and legal diversity among the subdivisions. There already are a bunch of countries that work like this, such as Malaysia, Nigeria and Belgium.