Thankfully, there are plenty of examples I've seen that serve much better as a representation of humanity.
|The Halo series provides the space command branch logo of a future UN that's actually halfway useful.|
|The Terran Dominion, while rather dystopian on founding as with most of the governments of Humanity, both on earth or in the Coprulu Sector, has a sweet logo that leaves no questions about the species militaristic nature.|
|The United Earth Directorate is the Starcraft world's current gov of Earth. Rather dystopian, but the flag is remarkably similar to that of the UNSC|
|And finally, the Aquila of the Imperium of Man. Makes the dystopias of other settings look darn Utopian.|