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
Source: I work on FedRAMP compliance for GCP Databases.
AWS US East-West (Northern Virginia, Ohio, Oregon, Northern California) is FedRAMP compliant at moderate impact level.
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.