Always more favourable travelling east (look at flight times between SIN and the east coast of Australia, or DRW-LHR) due to the meteorological conditions. SIN-NYC is far enough that it is favourable to continue around the globe to take advantage of this, even with the longer routing avoiding Russian airspace. Previously, sometimes NYC-SIN would take a polar route , sometimes it would track over Sweden (depending on conditions) but now it is a much more southerly route (a couple I looked at tracked over LHR/IST).
But consider the outbound route roughly via HND and compare to SIN-HND and HND-JFK flights. I picked some flights on same day on these routes, just to illustrate
SIN-HND 5:55, HND-JFK; 12:05, total 18 hrs flying time (this excludes taxi-ing but obviously includes take off, landing and ascent/descent)
JFK-HND 14:10, HND-SIN 6:45, total 20hrs 55 mins.
That's an extra 16% flying time! Compare to SIN-JFK 17:10 , JFK-SIN 18:30 (again random dates), only 8% extra flying time.