By Kanishka Singh and Barbara Goldberg NEW YORK (Reuters) -More than 1,400 U.S. flights were canceled on Sunday after the nation’s northeast states were walloped a day earlier by a deadly winter storm that prompted several states to declare emergencies. The total number of flight cancellations within, into, or out of the United States was about 1,450 as of Sunday afternoon, according to flight-tracking website FlightAware.com https://flightaware.com/live/cancelled. Another 1,774 U.S.-related flights were delayed, the data showed. LaGuardia Airport and John F. Kennedy International Airport in N…