Moody's downgrade of the U.S. credit rating made it the third of the three major ratings agencies to downgrade U.S. credit since 2011 amid widening budget deficits.

Yields in the Treasury market are rising, threatening to make it more expensive for consumers and the U.S. to manage debt.

The move came as Republicans seek to approve a large package of tax cuts, spending hikes and safety-net reductions which could add trillions of dollars in U.S. debt.

All three major U.S. stock market indexes rose Monday afternoon, following an earlier selloff sparked by long-dated Treasury yields surpassing the 5% mark after the financial ratings agency Moody’s downgraded the U.S. government’s credit rating late last week, citing rising debt and interest payment ratios.

Moody’s decision to lower the rating on U.S. government debt seems unlikely to shake up the corporate bond market too much.

If the U.S.’s loss of its final perfect credit rating boosts yields on Treasury debt, it likely would boost the cost of borrowing for both companies and consumers.

The U.S. government is spending far more than it takes in as revenue, causing ever-rising debt — and there is no sign that will change anytime soon. The big picture: Those facts are well-known to anybody who has taken a cursory look at the government's books.

CNBC's 'Mad Money' host and veteran market commentator Jim Cramer has urged investors not to get nervous in the face of concerns like the Moody’s downgrade of U.S. debt . The U.S.'s rising debt stands at $36 trillion as of now.