On rare occasion from NRT-SFO, I have seen the map show ground speed in excess of 1200km/hr = 745mph. Certainly it is not uncommon to exceed 1100kph = 680mph on this route, especially in winter.

Trans-pacific the jetstream is amazingly fast on occasion, but the same never seems to happen for me on SFO-LHR, I guess that over land it slows down!

Note that eastbound, people don't suffer through the same as a headwind as the aircraft takes a different route for precisely that reason.