The range for a fully-loaded 77L is only ~10,500 miles.

A nonstop SIN-SEA is quite doable for a 77L. SIN-LAX and SIN-MSP are in the neighborhood of ~9000 mi. A SIN-MSP route would be long but doable, but it would also have the advantage of providing a single connection for the vast majority of the US, and out of DL's major hubs.

SIN-JFK is 9500 mi, and SIN-ATL is 10,000 miles. Is Delta really going to reconfigure at least 3 77L's to an all-J (or mostly-J) configuration to reduce the weight and get a flight going in each direction, plus have one reserve for MX/WX, from the east coast? (Could you imagine the outcry if an all-J 77L got swapped for a Y+J 77L due to MX?)

http://www.gcmap.com/mapui?P=sin-sea...in-atl,sin-msp