"This downgrade is not that important and if you ask me, too silly. The U.S. is in a much better position than any, I repeat, any European country," Taylor added.
U.S. Treasury debt yields are also expected to rise on Monday. Yields on benchmark U.S. 10-year Treasury notes rebounded to 2.56 percent on Friday, but were not very far from a record low of near 2 percent hit during the throes of the 2007-09 global financial crisis.
"Be wary (Monday) of irrational depression as markets take flight," said Justin Urquhart Stewart, a director at Seven Investment Management in London. "We are dealing with the knowns and not the unknowns, but what we have a shortage of at the moment is political leadership."