Which nation does Kuvira come from?

Kuvira comes from the Earth Kingdom. She later rises as the kingdom's de facto leader and renames the state the Earth Empire.

Kuvira is an earthbender and metalbender who was orphaned as a child. Suyin Beifong brought her into the Zaofu community, where she became part of Suyin's extended household and served in the Zaofu Guard. Her upbringing in Zaofu strongly shaped her military discipline and political ambitions, but it does not change her national origin.

Viewers sometimes confuse Kuvira's background with Zaofu because she was raised there, or with the United Republic because she eventually tries to conquer Republic City. Those are places connected to her career, not her homeland. Her campaign begins as an effort to reunify the fractured Earth Kingdom after the Earth Queen's death, before becoming an authoritarian project to rule the territory herself.