Re: United Earth? No Thanks.
Surely the closest thing in todays world would be the EU. Sure most people in the EU might consider themselves British, French, Germany etc.. but they are also European Union citizens. And yes being a Eurpean Citizen does have real meaning, if a EU Citizen needs help abroad and their country doesn't have an Ambassador to that country and another EU member state does that member state is legally obligied to render aid.
On the continent of wild endeavour in the mountains of solace and solitude there stood the citadel of the time lords, the oldest and most mighty race in the universe looking down on the galaxies below sworn never to interfere only to watch.