Moody's Ratings downgraded the US credit rating, leading to a decline in US stocks and a rise in Treasury yields.The S&P 500 Index ETF fell by 1% post announcement to Aa1 from Aaa.Fitch Ratings and S&P Global Ratings also graded the US economy below the triple-A position.The risk of President Donald Trump's tariff regime adds to the economic uncertainty.Wall Street professionals express caution as tariffs may impact business and consumer confidence.Reacting to the news, experts predict caution in equity markets due to the US credit downgrade.The downgrade may affect other countries' sovereign debt as US Treasury bonds are considered a benchmark.Investors anticipate profit-taking in equities following the strong market rally.The downgrade signals concerns about the US fiscal dysfunction and tariff risks.The impact on stocks may be less severe compared to previous credit rating downgrades.