It had the most powerful Navy.
Benefits for Imperial Powers
Germany and Russia, which were ruled by Emperors, and so "imperial" powers. The so-called British Empire was really the leading world power at the time, but technically is was for the largest part a Kingdom; only in its colony India the British King had the title of Emperor.
France was the second largest imperial power, after the United Kingdom.
japan
Imperial Rome was the Roman Empire, which was the second largest empire antiquity saw and the 17th largest in history.
A competition between European imperial powers to control Africa
APEX - The imperial powers believed that they were spreading a superior culture in Africa and Asia
The greatest European powers included Rome, Holy Roman Empire, France, and the Byzantine Empire.
Japan and the United States
War Powers Act
No, London is the largest city in England
War Powers Act