Fitch is out saying that the US government shutdown does not have near term implications for its AA+/stable rating:
Regular reliance on continuing resolutions to keep government operations running shows continued weaknesses in U.S. fiscal policymaking.
Despite increased uncertainty around U.S. policy, expect the U.S. dollar’s predominant reserve currency status to continue for the foreseeable future.
Reversing previously enacted Medicaid cuts would not meaningfully impact near-term U.S. deficit forecasts.
Potential for a U.S. government shutdown to adversely affect economic growth would depend on its scope and duration.