As for me, I would like a republic governed by the penguins in Antarctica, because penguins are pretty cool! And maybe we can give the different aquatic species sovereignty over the ocean, because that would make international trade a lot more interesting.

As for countries run by humans, I would chop South Africa in half so we can create North Africa, it feels a bit mismatched otherwise. And all the little British and French bits scattered around the world should be independent, we would get a lot of extra countries! Except French Guiana, so we can still say that the longest land border of the French is with Brazil. At the very least, only the bits that don't touch Brazil can become independent (win-win situation in my opinion).

Quebec can do its own thing, and maybe some of the United States could become less united. There's not enough countries in continental North America. You could do the same with Brazil and Argentina too for South America, imagine, we could have so many more Guays along with Paraguay and Uruguay, maybe enough to complete the alphabet! Siberian Russia can be broken up, because it bothers me that there are many countries in Central, South, and East Asia, but only Russia in the North.