Public clouds are separated from their gov versions, with gov versions using older, modified versions of what everyone else uses. public clouds ARE NOT fedramp compliant
Not necessarily. Lots and lots of .gov operates in commercial clouds. Google doesn’t even have a distinct offering - just support add-ons for things like CJIS compliance. Microsoft’s footprint is a lot more complex.
Outside of the DoD space, the main distinctions between these offerings is where data can be stored and where and to what level of vetting vendor employees are.
Source: I work on FedRAMP compliance for GCP Databases.