The United Americas were formed in 2104 by the merging of North, Central and South America into one socio-economic block. The creation of the United Americas was largely brought about by the emergence and growth of the Three World Empire, which was at the time pioneering space exploration and extra-planetary colonization. Aside from its terrestrial presence, the UA also oversaw several extra-planetary colonies, including that of Olympia on Luna.
The United States of America's position as a starfaring, colonizing power has ensured it a leading role in the structure of the United Americas, as evidence from the name of the United States Colonial Marine Corps. The USCM is fully integrated into the joint command structure of the United Americas Allied Command and forms the major striking element of the UA forces.