Would another AAA rating downgrade be serious for the US?

AFP :
The possible loss of its AAA rating from Fitch would be a symbolic blow for the United States as it finds itself on the brink of a debt default because of a political impasse.
Such a downgrade is not unprecedented — S&P Global yanked Washington’s AAA rating during the 2011 showdown over the debt limit — and would probably have few immediate consequences for the world’s biggest economy, whose debt is highly sought after on the markets.
AAA rating is the top rating assigned by credit ratings agencies on debt issued by governments and companies.
The three main ratings agencies — S&P Global, Fitch and Moody’s — use a letter system ranging from AAA to D (for defaults), passing through B and C.
They are an indication for investors of entities’ capacity to repay their debts.