Here are some options depending on the specific context:
* Administration: This is a general term for a group of people who manage and run a government.
* Bureaucracy: This emphasizes the large, complex, and often inflexible structure of a government.
* Cabinet: This is a specific group of high-ranking government officials, often advising the head of state.
* Government: This is the most general term and refers to the entire system of governing a country.
* Regime: This term is often used to describe a particular government, especially one that is authoritarian or oppressive.
You can also use body, department, or agency to refer to specific parts of a government.
Ultimately, the best collective noun will depend on the specific context and the specific governmental organization you are referring to.