Much US carrier service into HKG pre-2000 was UA and NW serving via other hubs, mostly Japan. Seems like the first nonstop service from the NYC area to HKG was CO in 2001

https://en.wikipedia.org/wiki/Longest_flights

Aircraft range was going to limit where in Asia an airline could serve from the US without fifth freedom rights.

AA's service to Asia was very thin before 2010 or so. For a while it was Japan only from a few hubs, mostly NRT but some service to KIX and NGO.

Interesting how BOS's importance has yo-yoed in AA's recent history. That's a decent network shown in 2000. Quite a bit of transcon service, and AA offered both day and night flights to LHR. But things scaled back, then took a hit in the financial crisis until they were roughly back to service to the "cornerstone hubs" (remember them?). I was especially worried about Boston's viability when they closed the Eagle operations. But then the US merger made BOS important again, along with way more nonstop OneWorld service to Europe and Asia than I ever dreamed of.