The Imperial Federation proposal was a plan put forward in the late 19th and early 20th centuries to create a federal union between Great Britain and the British colonies, including Canada, Australia, New Zealand, and South Africa. The idea was to create a single imperial state that would be unified by shared institutions, such as a central parliament and a common military and foreign policy.
Ultimately, the idea would fade away, but this flag is an attempt at picturing what a flag for this proposed state could have been, assuming it survived into the 21st century and somehow incorporated the United States.
The arms on the shield are as follows clockwise:
England
Scotland
Wales
Ireland
Australia
Oregon Cascadia
Columbia
South Africa
West Indies
Dixieland
Canada