However, standard course of action for these things is to form an alliance. Europe all didn't merge into one state after WWII, despite the fact that they were hammered to the ground viciously. People want their states to be independent. They want security but also their own governance - an alliance can handle that, just like NATO did and still does. 

This is a problem that I have with every super state here. Aaron, I'm sure, agrees as well. Alliances, yes. Large scale annexations, however, are rarely peaceful or deemed beneficial to both parties.