LONDON--(BUSINESS WIRE)--A US government shutdown would not have a direct impact on the sovereign's 'AAA'/Stable rating, Fitch Ratings says. Its main implication for the US's sovereign creditworthiness would depend on whether it foreshadowed a destabilisation of US budget policymaking, including brinkmanship over the federal debt limit. The US risks a federal government shutdown if Congress does not pass funding legislation by the end of the current fiscal year on September 30 (just six of the