The Unified Earth was a period of Earth history beginning in the late 2060s and continuing much longer. Following a global war which nearly threatened to destroy the planet itself, all 194 nations on Earth agreed to a ceasefire, and global co-operation on major issues.
The Tenth Doctor was fond of the Unified Earth, stating that one could find a “decent cup of tea, a custard cream, and a good book” anywhere on Earth. However, he was less fond of the fact that fries were more popular than thicker, greasier chips, and rarely had enough vinegar. (PROSE: Total Eclipse of the Heart)