NW isn't bad but the times are awful. You get in at 1 am and the SIN-NRT-United States flight leaves at 6 am.

SQ has similarly timed flights but also better ones. They have some that get in late morning and leave for the US in the mid morning. They also have the LAX and EWR non-stops that are timed more for the NY and LA people but aren't bad for others going to other US cities. The coach seats on the non-stops are better than coach with about 5 inches more legroom and better services. It's sort of like Coach plus or Business minus. It's called Executive Economy. There is no regular coach or cattle class on the nonstops.