Jack of Harts

The South American Union is well-named. It is a union of independent Nation States. They have a Union Council, and each State in South America and each off world colony has a single seat on it. They elect a President from their number who is authorized to perform foreign relations and run a military much like many nations. But a simple majority vote of the council can abrogate any decision made by the President. Or remove the President altogether. Of course each Councilor only serves a single four-year term, with a quarter of them replaced each year to make certain there is a constant influx of new blood and the old blood are soon retired. This keeps the central government from growing too big for the States to keep in check.