WASHINGTON (Reuters) -Moody's downgrade of the U.S. sovereign credit rating has elicited mixed responses among Republicans in Congress, with some questioning the motive behind the change and others depicting it as a warning that lawmakers should heed as they wrestle with a sweeping tax and budget bill. The downgrade, announced on Friday evening, came only hours after a handful of Republicans on the U.S. House of Representatives' budget committee blocked progress of President Donald Trump's tax and spending legislation due to their concerns of its potential to balloon the federal deficit. The credit rater is the last of the major ratings agencies to strip the U.S. of the highest rating of AAA.